diff -r 198edd926751 Doc/library/typing.rst
--- a/Doc/library/typing.rst	Sat Jan 07 09:32:56 2017 +0300
+++ b/Doc/library/typing.rst	Sat Jan 07 13:36:51 2017 -0800
@@ -678,6 +678,37 @@
               yield start
               start += 1
 
+.. class:: AsyncGenerator(AsyncIterator[T_co], Generic[T_co, T_contra])
+
+  An async generator can be annotated by the generic type
+  ``AsyncGenerator[YieldType, SendType]``. For example::
+
+    async def echo_round() -> AsyncGenerator[int, float]:
+        sent = yield 0
+        while sent >= 0.0:
+            rounded = await round(sent)
+            sent = yield rounded
+
+  Unlike normal generators, async generators cannot return a value, so there
+  is no ``ReturnType`` type parameter. As with :class:`Generator`, the
+  ``SendType`` behaves contravariantly.
+
+  If your generator will only yield values, set the ``SendType`` to
+  ``None``::
+
+    async def infinite_stream(start: int) -> AsyncGenerator[int, None]:
+        while True:
+            yield start
+            start = await increment(start)
+
+  Alternatively, annotate your generator as having a return type of
+  either ``AsyncIterable[YieldType]`` or ``AsyncIterator[YieldType]``::
+
+    async def infinite_stream(start: int) -> AsyncIterator[int]:
+        while True:
+            yield start
+            start = await increment(start)
+
 .. class:: Text
 
    ``Text`` is an alias for ``str``. It is provided to supply a forward