Abstract: A diaphragm compressor includes a cylindrical piston and an annular diaphragm member with a central hub secured by a grommet within an annular recess in the piston face. The outer peripheral edge of the diaphragm is affixed between a clamp ring and a valve plate which has a central recess to form a compression chamber. The diaphragm has a convolution which opens toward the compression chamber. The valve plate has a projection complementing and mating with the convolution. A plurality of circumferentially spaced and radial intake ports lead to an annular piston intake opening inwardly of the diaphragm. A flexible, tee-shaped valve member includes a stem locked within the piston with a planar sealing disc having an outer bead abutting the inner piston face and overlying the intake opening. The stem may pass through a central opening with an outer stem enlargement creating a resilient clamping of the valve member to a holding portion of the piston.