diff --git a/Lib/ftplib.py b/Lib/ftplib.py
--- a/Lib/ftplib.py
+++ b/Lib/ftplib.py
@@ -54,6 +54,8 @@
 
 # The standard FTP server control port
 FTP_PORT = 21
+# The sizehint parameter passed to readline() calls
+MAXLINE = 8192
 
 
 # Exception raised when an error or invalid response is received
@@ -62,11 +64,15 @@
 class error_temp(Error): pass           # 4xx errors
 class error_perm(Error): pass           # 5xx errors
 class error_proto(Error): pass          # response does not begin with [1-5]
+class LineTooLong(Error):
+    def __init__(self, nbytes):
+        Error.__init__(self, "got more than %d bytes" % nbytes)
+
 
 
 # All exceptions (hopefully) that may be raised here and that aren't
 # (always) programming errors on our side
-all_errors = (Error, IOError, EOFError)
+all_errors = (Error, IOError, EOFError, LineTooLong)
 
 
 # Line terminators (we always output CRLF, but accept any of CRLF, CR, LF)
@@ -100,6 +106,7 @@
     debugging = 0
     host = ''
     port = FTP_PORT
+    maxline = MAXLINE
     sock = None
     file = None
     welcome = None
@@ -179,7 +186,9 @@
     # Internal: return one line from the server, stripping CRLF.
     # Raise EOFError if the connection is closed
     def getline(self):
-        line = self.file.readline()
+        line = self.file.readline(self.maxline + 1)
+        if len(line) > self.maxline:
+            raise LineTooLong(self.maxline)
         if self.debugging > 1:
             print '*get*', self.sanitize(line)
         if not line: raise EOFError
@@ -421,7 +430,9 @@
         conn = self.transfercmd(cmd)
         fp = conn.makefile('rb')
         while 1:
-            line = fp.readline()
+            line = fp.readline(self.maxline + 1)
+            if len(line) > self.maxline:
+                raise LineTooLong(self.maxline)
             if self.debugging > 2: print '*retr*', repr(line)
             if not line:
                 break
@@ -473,7 +484,9 @@
         self.voidcmd('TYPE A')
         conn = self.transfercmd(cmd)
         while 1:
-            buf = fp.readline()
+            buf = fp.readline(self.maxline + 1)
+            if len(buf) > self.maxline:
+                raise LineTooLong(self.maxline)
             if not buf: break
             if buf[-2:] != CRLF:
                 if buf[-1] in CRLF: buf = buf[:-1]
diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
--- a/Lib/test/test_ftplib.py
+++ b/Lib/test/test_ftplib.py
@@ -46,6 +46,7 @@
         self.last_received_cmd = None
         self.last_received_data = ''
         self.next_response = ''
+        self.next_retr_data = ''
         self.push('220 welcome')
 
     def collect_incoming_data(self, data):
@@ -162,7 +163,7 @@
 
     def cmd_retr(self, arg):
         self.push('125 retr ok')
-        self.dtp.push(RETR_DATA)
+        self.dtp.push(self.next_retr_data or RETR_DATA)
         self.dtp.close_when_done()
 
     def cmd_list(self, arg):
@@ -362,6 +363,20 @@
         # IPv4 is in use, just make sure send_epsv has not been used
         self.assertEqual(self.server.handler.last_received_cmd, 'pasv')
 
+    def test_line_too_long(self):
+        self.assertRaises(ftplib.LineTooLong, self.client.sendcmd,
+                          'x' * self.client.maxline * 2)
+
+    def test_retrlines_too_long(self):
+        self.server.handler.next_retr_data = 'x' * self.client.maxline * 2
+        received = []
+        self.assertRaises(ftplib.LineTooLong,
+                          self.client.retrlines, 'retr', received.append)
+
+    def test_storlines_too_long(self):
+        f = StringIO.StringIO('x' * self.client.maxline * 2)
+        self.assertRaises(ftplib.LineTooLong, self.client.storlines, 'stor', f)
+
 
 class TestIPv6Environment(TestCase):