This disclosure relates to a pressure regulator formed from a one-piece flexible diaphragm and valve member structure wherein the flexible valve member is disposed spaced from one side of the flexible diaphragm so that the flexible valve member can be flexed through a valve seat of a housing to open and close the valve seat on one side thereof while the flexible diaphragm is disposed on the other side of the valve seat and can be utilized to cooperate with the housing structure carrying the valve seat to define a chamber therewith.