The properties of a pressure transducer consisting of a single-crystal silicon diaphragm having stress-sensitivepiezoresistive regions formed by the localized diffusion of impurities have been theoretically andexperimentally investigated. The longitudinal and transverse piezoresistance effects are discussed and theresults are applied to the stress pattern of a deformed diaphragm. The conditions under which the stress inthe diaphragm varies linearly with applied pressure are discussed and good agreement between the predictedand measured sensitivity is found in both the linear and nonlinear cases.