Abstract: A diaphragm valve comprises a valve sub-assembly including a diaphragm secured to a valve body by a clamping member. The clamping member is provided with screw threads on to which a drive assembly is screwed to complete the valve. The drive assembly may be a piston and cylinder drive assembly or a handwheel drive assembly. An indicator module to provide an indication of whether the valve is open or closed can be incorporated between the clamping member and the drive assembly. The drive assembly can be removed for service or interchanged without disturbing the fluid seal between the diaphragm and the valve body.