diff --git a/postgres-protocol/src/message/frontend.rs b/postgres-protocol/src/message/frontend.rs
index 0ff0ddb6..6daed7d9 100644
--- a/postgres-protocol/src/message/frontend.rs
+++ b/postgres-protocol/src/message/frontend.rs
@@ -2,6 +2,8 @@
 #![allow(missing_docs)]
 
 use byteorder::{BigEndian, ByteOrder, WriteBytesExt};
+use bytes::{Buf, BufMut, BytesMut, IntoBuf};
+use std::convert::TryFrom;
 use std::error::Error;
 use std::io;
 use std::marker;
@@ -263,6 +265,40 @@ pub fn copy_data(data: &[u8], buf: &mut Vec<u8>) -> io::Result<()> {
     })
 }
 
+pub struct CopyData<T> {
+    buf: T,
+    len: i32,
+}
+
+impl<T> CopyData<T>
+where
+    T: Buf,
+{
+    pub fn new<U>(buf: U) -> io::Result<CopyData<T>>
+    where
+        U: IntoBuf<Buf = T>,
+    {
+        let buf = buf.into_buf();
+
+        let len = buf
+            .remaining()
+            .checked_add(4)
+            .and_then(|l| i32::try_from(l).ok())
+            .ok_or_else(|| {
+                io::Error::new(io::ErrorKind::InvalidInput, "message length overflow")
+            })?;
+
+        Ok(CopyData { buf, len })
+    }
+
+    pub fn write(self, out: &mut BytesMut) {
+        out.reserve(self.len as usize + 1);
+        out.put_u8(b'd');
+        out.put_i32_be(self.len);
+        out.put(self.buf);
+    }
+}
+
 #[inline]
 pub fn copy_done(buf: &mut Vec<u8>) {
     buf.push(b'c');
diff --git a/tokio-postgres/src/impls.rs b/tokio-postgres/src/impls.rs
index 546c3d7d..520a4aff 100644
--- a/tokio-postgres/src/impls.rs
+++ b/tokio-postgres/src/impls.rs
@@ -170,7 +170,7 @@ pub struct CopyIn<S>(pub(crate) proto::CopyInFuture<S>)
 where
     S: Stream,
     S::Item: IntoBuf,
-    <S::Item as IntoBuf>::Buf: Send,
+    <S::Item as IntoBuf>::Buf: 'static + Send,
     S::Error: Into<Box<dyn error::Error + Sync + Send>>;
 
 impl<S> Future for CopyIn<S>
diff --git a/tokio-postgres/src/lib.rs b/tokio-postgres/src/lib.rs
index 060e0c5d..78c65331 100644
--- a/tokio-postgres/src/lib.rs
+++ b/tokio-postgres/src/lib.rs
@@ -242,7 +242,7 @@ impl Client {
     where
         S: Stream,
         S::Item: IntoBuf,
-        <S::Item as IntoBuf>::Buf: Send,
+        <S::Item as IntoBuf>::Buf: 'static + Send,
         // FIXME error type?
         S::Error: Into<Box<dyn StdError + Sync + Send>>,
     {
diff --git a/tokio-postgres/src/proto/client.rs b/tokio-postgres/src/proto/client.rs
index a328e90d..abb2f534 100644
--- a/tokio-postgres/src/proto/client.rs
+++ b/tokio-postgres/src/proto/client.rs
@@ -11,6 +11,7 @@ use std::sync::{Arc, Weak};
 use tokio_io::{AsyncRead, AsyncWrite};
 
 use crate::proto::bind::BindFuture;
+use crate::proto::codec::FrontendMessage;
 use crate::proto::connection::{Request, RequestMessages};
 use crate::proto::copy_in::{CopyInFuture, CopyInReceiver, CopyMessage};
 use crate::proto::copy_out::CopyOutStream;
@@ -185,8 +186,12 @@ impl Client {
         if let Ok(ref mut buf) = buf {
             frontend::sync(buf);
         }
-        let pending =
-            PendingRequest(buf.map(|m| (RequestMessages::Single(m), self.0.idle.guard())));
+        let pending = PendingRequest(buf.map(|m| {
+            (
+                RequestMessages::Single(FrontendMessage::Raw(m)),
+                self.0.idle.guard(),
+            )
+        }));
         BindFuture::new(self.clone(), pending, name, statement.clone())
     }
 
@@ -208,12 +213,12 @@ impl Client {
     where
         S: Stream,
         S::Item: IntoBuf,
-        <S::Item as IntoBuf>::Buf: Send,
+        <S::Item as IntoBuf>::Buf: 'static + Send,
         S::Error: Into<Box<dyn StdError + Sync + Send>>,
     {
         let (mut sender, receiver) = mpsc::channel(1);
         let pending = PendingRequest(self.excecute_message(statement, params).map(|data| {
-            match sender.start_send(CopyMessage { data, done: false }) {
+            match sender.start_send(CopyMessage::Message(data)) {
                 Ok(AsyncSink::Ready) => {}
                 _ => unreachable!("channel should have capacity"),
             }
@@ -278,7 +283,7 @@ impl Client {
         frontend::sync(&mut buf);
         let (sender, _) = mpsc::channel(0);
         let _ = self.0.sender.unbounded_send(Request {
-            messages: RequestMessages::Single(buf),
+            messages: RequestMessages::Single(FrontendMessage::Raw(buf)),
             sender,
             idle: None,
         });
@@ -326,11 +331,11 @@ impl Client {
         &self,
         statement: &Statement,
         params: &[&dyn ToSql],
-    ) -> Result<Vec<u8>, Error> {
+    ) -> Result<FrontendMessage, Error> {
         let mut buf = self.bind_message(statement, "", params)?;
         frontend::execute("", 0, &mut buf).map_err(Error::parse)?;
         frontend::sync(&mut buf);
-        Ok(buf)
+        Ok(FrontendMessage::Raw(buf))
     }
 
     fn pending<F>(&self, messages: F) -> PendingRequest
@@ -338,8 +343,11 @@ impl Client {
         F: FnOnce(&mut Vec<u8>) -> Result<(), Error>,
     {
         let mut buf = vec![];
-        PendingRequest(
-            messages(&mut buf).map(|()| (RequestMessages::Single(buf), self.0.idle.guard())),
-        )
+        PendingRequest(messages(&mut buf).map(|()| {
+            (
+                RequestMessages::Single(FrontendMessage::Raw(buf)),
+                self.0.idle.guard(),
+            )
+        }))
     }
 }
diff --git a/tokio-postgres/src/proto/codec.rs b/tokio-postgres/src/proto/codec.rs
index 4e37ab60..c7c6d904 100644
--- a/tokio-postgres/src/proto/codec.rs
+++ b/tokio-postgres/src/proto/codec.rs
@@ -1,16 +1,26 @@
-use bytes::BytesMut;
+use bytes::{Buf, BytesMut};
 use postgres_protocol::message::backend;
+use postgres_protocol::message::frontend::CopyData;
 use std::io;
 use tokio_codec::{Decoder, Encoder};
 
+pub enum FrontendMessage {
+    Raw(Vec<u8>),
+    CopyData(CopyData<Box<dyn Buf + Send>>),
+}
+
 pub struct PostgresCodec;
 
 impl Encoder for PostgresCodec {
-    type Item = Vec<u8>;
+    type Item = FrontendMessage;
     type Error = io::Error;
 
-    fn encode(&mut self, item: Vec<u8>, dst: &mut BytesMut) -> Result<(), io::Error> {
-        dst.extend_from_slice(&item);
+    fn encode(&mut self, item: FrontendMessage, dst: &mut BytesMut) -> Result<(), io::Error> {
+        match item {
+            FrontendMessage::Raw(buf) => dst.extend_from_slice(&buf),
+            FrontendMessage::CopyData(data) => data.write(dst),
+        }
+
         Ok(())
     }
 }
diff --git a/tokio-postgres/src/proto/connect_raw.rs b/tokio-postgres/src/proto/connect_raw.rs
index 45b2c3e5..85368cd9 100644
--- a/tokio-postgres/src/proto/connect_raw.rs
+++ b/tokio-postgres/src/proto/connect_raw.rs
@@ -11,7 +11,7 @@ use std::collections::HashMap;
 use tokio_codec::Framed;
 use tokio_io::{AsyncRead, AsyncWrite};
 
-use crate::proto::{Client, Connection, MaybeTlsStream, PostgresCodec, TlsFuture};
+use crate::proto::{Client, Connection, MaybeTlsStream, PostgresCodec, TlsFuture, FrontendMessage};
 use crate::tls::ChannelBinding;
 use crate::{Config, Error, TlsConnect};
 
@@ -111,7 +111,7 @@ where
         let stream = Framed::new(stream, PostgresCodec);
 
         transition!(SendingStartup {
-            future: stream.send(buf),
+            future: stream.send(FrontendMessage::Raw(buf)),
             config: state.config,
             idx: state.idx,
             channel_binding,
@@ -156,7 +156,7 @@ where
                 let mut buf = vec![];
                 frontend::password_message(pass, &mut buf).map_err(Error::encode)?;
                 transition!(SendingPassword {
-                    future: state.stream.send(buf),
+                    future: state.stream.send(FrontendMessage::Raw(buf)),
                     config: state.config,
                     idx: state.idx,
                 })
@@ -178,7 +178,7 @@ where
                 let mut buf = vec![];
                 frontend::password_message(output.as_bytes(), &mut buf).map_err(Error::encode)?;
                 transition!(SendingPassword {
-                    future: state.stream.send(buf),
+                    future: state.stream.send(FrontendMessage::Raw(buf)),
                     config: state.config,
                     idx: state.idx,
                 })
@@ -235,7 +235,7 @@ where
                     .map_err(Error::encode)?;
 
                 transition!(SendingSasl {
-                    future: state.stream.send(buf),
+                    future: state.stream.send(FrontendMessage::Raw(buf)),
                     scram,
                     config: state.config,
                     idx: state.idx,
@@ -293,7 +293,7 @@ where
                 let mut buf = vec![];
                 frontend::sasl_response(state.scram.message(), &mut buf).map_err(Error::encode)?;
                 transition!(SendingSasl {
-                    future: state.stream.send(buf),
+                    future: state.stream.send(FrontendMessage::Raw(buf)),
                     scram: state.scram,
                     config: state.config,
                     idx: state.idx,
diff --git a/tokio-postgres/src/proto/connection.rs b/tokio-postgres/src/proto/connection.rs
index dd9f30fe..14559fd0 100644
--- a/tokio-postgres/src/proto/connection.rs
+++ b/tokio-postgres/src/proto/connection.rs
@@ -8,17 +8,17 @@ use std::io;
 use tokio_codec::Framed;
 use tokio_io::{AsyncRead, AsyncWrite};
 
-use crate::proto::codec::PostgresCodec;
+use crate::proto::codec::{FrontendMessage, PostgresCodec};
 use crate::proto::copy_in::CopyInReceiver;
 use crate::proto::idle::IdleGuard;
 use crate::{AsyncMessage, Notification};
 use crate::{DbError, Error};
 
 pub enum RequestMessages {
-    Single(Vec<u8>),
+    Single(FrontendMessage),
     CopyIn {
         receiver: CopyInReceiver,
-        pending_message: Option<Vec<u8>>,
+        pending_message: Option<FrontendMessage>,
     },
 }
 
@@ -188,7 +188,7 @@ where
                     self.state = State::Terminating;
                     let mut request = vec![];
                     frontend::terminate(&mut request);
-                    RequestMessages::Single(request)
+                    RequestMessages::Single(FrontendMessage::Raw(request))
                 }
                 Async::Ready(None) => {
                     trace!(
diff --git a/tokio-postgres/src/proto/copy_in.rs b/tokio-postgres/src/proto/copy_in.rs
index 33018aa1..80f09c52 100644
--- a/tokio-postgres/src/proto/copy_in.rs
+++ b/tokio-postgres/src/proto/copy_in.rs
@@ -1,20 +1,21 @@
-use bytes::{Buf, IntoBuf};
+use bytes::{Buf, BufMut, BytesMut, IntoBuf};
 use futures::sink;
+use futures::stream;
 use futures::sync::mpsc;
 use futures::{try_ready, Async, AsyncSink, Future, Poll, Sink, Stream};
 use postgres_protocol::message::backend::Message;
-use postgres_protocol::message::frontend;
+use postgres_protocol::message::frontend::{self, CopyData};
 use state_machine_future::{transition, RentToOwn, StateMachineFuture};
 use std::error::Error as StdError;
-use std::mem;
 
 use crate::proto::client::{Client, PendingRequest};
+use crate::proto::codec::FrontendMessage;
 use crate::proto::statement::Statement;
 use crate::Error;
 
-pub struct CopyMessage {
-    pub data: Vec<u8>,
-    pub done: bool,
+pub enum CopyMessage {
+    Message(FrontendMessage),
+    Done,
 }
 
 pub struct CopyInReceiver {
@@ -32,30 +33,29 @@ impl CopyInReceiver {
 }
 
 impl Stream for CopyInReceiver {
-    type Item = Vec<u8>;
+    type Item = FrontendMessage;
     type Error = ();
 
-    fn poll(&mut self) -> Poll<Option<Vec<u8>>, ()> {
+    fn poll(&mut self) -> Poll<Option<FrontendMessage>, ()> {
         if self.done {
             return Ok(Async::Ready(None));
         }
 
         match self.receiver.poll()? {
-            Async::Ready(Some(mut data)) => {
-                if data.done {
-                    self.done = true;
-                    frontend::copy_done(&mut data.data);
-                    frontend::sync(&mut data.data);
-                }
-
-                Ok(Async::Ready(Some(data.data)))
+            Async::Ready(Some(CopyMessage::Message(message))) => Ok(Async::Ready(Some(message))),
+            Async::Ready(Some(CopyMessage::Done)) => {
+                self.done = true;
+                let mut buf = vec![];
+                frontend::copy_done(&mut buf);
+                frontend::sync(&mut buf);
+                Ok(Async::Ready(Some(FrontendMessage::Raw(buf))))
             }
             Async::Ready(None) => {
                 self.done = true;
                 let mut buf = vec![];
                 frontend::copy_fail("", &mut buf).unwrap();
                 frontend::sync(&mut buf);
-                Ok(Async::Ready(Some(buf)))
+                Ok(Async::Ready(Some(FrontendMessage::Raw(buf))))
             }
             Async::NotReady => Ok(Async::NotReady),
         }
@@ -67,7 +67,7 @@ pub enum CopyIn<S>
 where
     S: Stream,
     S::Item: IntoBuf,
-    <S::Item as IntoBuf>::Buf: Send,
+    <S::Item as IntoBuf>::Buf: 'static + Send,
     S::Error: Into<Box<dyn StdError + Sync + Send>>,
 {
     #[state_machine_future(start, transitions(ReadCopyInResponse))]
@@ -86,8 +86,8 @@ where
     },
     #[state_machine_future(transitions(WriteCopyDone))]
     WriteCopyData {
-        stream: S,
-        buf: Vec<u8>,
+        stream: stream::Fuse<S>,
+        buf: BytesMut,
         pending_message: Option<CopyMessage>,
         sender: mpsc::Sender<CopyMessage>,
         receiver: mpsc::Receiver<Message>,
@@ -109,7 +109,7 @@ impl<S> PollCopyIn<S> for CopyIn<S>
 where
     S: Stream,
     S::Item: IntoBuf,
-    <S::Item as IntoBuf>::Buf: Send,
+    <S::Item as IntoBuf>::Buf: 'static + Send,
     S::Error: Into<Box<dyn StdError + Sync + Send>>,
 {
     fn poll_start<'a>(state: &'a mut RentToOwn<'a, Start<S>>) -> Poll<AfterStart<S>, Error> {
@@ -135,8 +135,8 @@ where
                 Some(Message::CopyInResponse(_)) => {
                     let state = state.take();
                     transition!(WriteCopyData {
-                        stream: state.stream,
-                        buf: vec![],
+                        stream: state.stream.fuse(),
+                        buf: BytesMut::new(),
                         pending_message: None,
                         sender: state.sender,
                         receiver: state.receiver
@@ -167,44 +167,51 @@ where
         }
 
         loop {
-            let done = loop {
+            let buf: Box<dyn Buf + Send> = loop {
                 match try_ready!(state.stream.poll().map_err(Error::copy_in_stream)) {
-                    Some(data) => {
-                        // FIXME avoid collect
-                        frontend::copy_data(&data.into_buf().collect::<Vec<_>>(), &mut state.buf)
-                            .map_err(Error::encode)?;
+                    Some(buf) => {
+                        let buf = buf.into_buf();
+                        if buf.remaining() > 4096 {
+                            if state.buf.is_empty() {
+                                break Box::new(buf);
+                            } else {
+                                let cur_buf = state.buf.take().freeze().into_buf();
+                                break Box::new(cur_buf.chain(buf));
+                            }
+                        }
+
+                        state.buf.reserve(buf.remaining());
+                        state.buf.put(buf);
                         if state.buf.len() > 4096 {
-                            break false;
+                            break Box::new(state.buf.take().freeze().into_buf());
                         }
                     }
-                    None => break true,
+                    None => break Box::new(state.buf.take().freeze().into_buf()),
                 }
             };
 
-            let message = CopyMessage {
-                data: mem::replace(&mut state.buf, vec![]),
-                done,
-            };
+            if buf.has_remaining() {
+                let data = CopyData::new(buf).map_err(Error::encode)?;
+                let message = CopyMessage::Message(FrontendMessage::CopyData(data));
 
-            if done {
+                match state
+                    .sender
+                    .start_send(message)
+                    .map_err(|_| Error::closed())?
+                {
+                    AsyncSink::Ready => {}
+                    AsyncSink::NotReady(message) => {
+                        state.pending_message = Some(message);
+                        return Ok(Async::NotReady);
+                    }
+                }
+            } else {
                 let state = state.take();
                 transition!(WriteCopyDone {
-                    future: state.sender.send(message),
+                    future: state.sender.send(CopyMessage::Done),
                     receiver: state.receiver,
                 });
             }
-
-            match state
-                .sender
-                .start_send(message)
-                .map_err(|_| Error::closed())?
-            {
-                AsyncSink::Ready => {}
-                AsyncSink::NotReady(message) => {
-                    state.pending_message = Some(message);
-                    return Ok(Async::NotReady);
-                }
-            }
         }
     }
 
diff --git a/tokio-postgres/src/proto/mod.rs b/tokio-postgres/src/proto/mod.rs
index 7667901c..7c30cda8 100644
--- a/tokio-postgres/src/proto/mod.rs
+++ b/tokio-postgres/src/proto/mod.rs
@@ -53,7 +53,7 @@ pub use crate::proto::bind::BindFuture;
 pub use crate::proto::cancel_query::CancelQueryFuture;
 pub use crate::proto::cancel_query_raw::CancelQueryRawFuture;
 pub use crate::proto::client::Client;
-pub use crate::proto::codec::PostgresCodec;
+pub use crate::proto::codec::{FrontendMessage, PostgresCodec};
 #[cfg(feature = "runtime")]
 pub use crate::proto::connect::ConnectFuture;
 #[cfg(feature = "runtime")]
diff --git a/tokio-postgres/tests/test/main.rs b/tokio-postgres/tests/test/main.rs
index 7930b1b9..06a6d738 100644
--- a/tokio-postgres/tests/test/main.rs
+++ b/tokio-postgres/tests/test/main.rs
@@ -4,6 +4,7 @@ use futures::sync::mpsc;
 use futures::{future, stream, try_ready};
 use log::debug;
 use std::error::Error;
+use std::fmt::Write;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::time::{Duration, Instant};
 use tokio::net::TcpStream;
@@ -616,6 +617,49 @@ fn copy_in() {
     assert_eq!(rows[1].get::<_, &str>(1), "joe");
 }
 
+#[test]
+fn copy_in_large() {
+    let _ = env_logger::try_init();
+    let mut runtime = Runtime::new().unwrap();
+
+    let (mut client, connection) = runtime.block_on(connect("user=postgres")).unwrap();
+    let connection = connection.map_err(|e| panic!("{}", e));
+    runtime.handle().spawn(connection).unwrap();
+
+    runtime
+        .block_on(
+            client
+                .simple_query(
+                    "CREATE TEMPORARY TABLE foo (
+                        id INTEGER,
+                        name TEXT
+                    )",
+                )
+                .for_each(|_| Ok(())),
+        )
+        .unwrap();
+
+    let a = "0\tname0\n".to_string();
+    let mut b = String::new();
+    for i in 1..5_000 {
+        writeln!(b, "{0}\tname{0}", i).unwrap();
+    }
+    let mut c = String::new();
+    for i in 5_000..10_000 {
+        writeln!(c, "{0}\tname{0}", i).unwrap();
+    }
+
+    let stream = stream::iter_ok::<_, String>(vec![a, b, c]);
+    let rows = runtime
+        .block_on(
+            client
+                .prepare("COPY foo FROM STDIN")
+                .and_then(|s| client.copy_in(&s, &[], stream)),
+        )
+        .unwrap();
+    assert_eq!(rows, 10_000);
+}
+
 #[test]
 fn copy_in_error() {
     let _ = env_logger::try_init();