Abstract: An inhalation valve is provided for testing the breathing capacity of a person. The valve is constructed of two plastic moldings which snap together and trap a flexible elastomeric valve diaphragm between them. The valve is provided with a mouthpipe. Exhalation through the mouthpipe deflects the diaphragm to permit substantially unrestricted exhalation. Inhalation is through a laterally displaced passageway having a transverse wall therein to produce a pressure drop. Tubular fittings are provided in the pressure drop area behind the wall and exteriorally of the flow path to provide an input to an electronic apparatus to indicate the efficiency of breathing.