diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 95a85cefdd2..1a9dd9d390a 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -639,6 +639,11 @@ Instances of the :class:`Popen` class have the following methods:
    .. versionchanged:: 3.3
       *timeout* was added.
 
+   .. deprecated:: 3.4
+
+      Do not use the undocumented *endtime* parameter.  It is was
+      unintentionally exposed in 3.3 but was intended to be private
+      for internal use.  Use *timeout* instead.
 
 .. method:: Popen.communicate(input=None, timeout=None)