Flagging master as 1.0.0-pre1.
diff --git a/src/python/grpcio/grpc_version.py b/src/python/grpcio/grpc_version.py
index 0f4db9d..d1e2d41 100644
--- a/src/python/grpcio/grpc_version.py
+++ b/src/python/grpcio/grpc_version.py
@@ -29,4 +29,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio/grpc_version.py.template`!!!
 
-VERSION='0.16.0.dev0'
+VERSION='1.0.0rc1'
diff --git a/src/python/grpcio_tests/grpc_version.py b/src/python/grpcio_tests/grpc_version.py
index 7aa6007..a238785 100644
--- a/src/python/grpcio_tests/grpc_version.py
+++ b/src/python/grpcio_tests/grpc_version.py
@@ -29,4 +29,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_tests/grpc_version.py.template`!!!
 
-VERSION='0.16.0.dev0'
+VERSION='1.0.0rc1'