A computer program to calculate and interpret the standard pulmonary function tests has been developed on a programmable calculator system. The program computes both predicted and measured values for static and dynamic lung volumes, airways resistance and diffusing capacity. It then checks for differences between predicted and obtained values and interprets them according to a specific, clinically useful set of diagnostic criteria. By acquisition of a reliable and easy-to-use data processing system, a pulmonary function laboratory can significantly increase the efficiency and accuracy of its day-to-day work.