A software package has been developed to interpret exercise test data recorded by a metabolic measurement cart (MMC). This package reduces and interprets the exercise test data relative to population and patient specific criteria. The data flow for the data reduction and report printing is described. The data structures used in this processing are illustrated. The application of structured programming, a real-time executive and an easy-to-read language--such as Pascal--is illustrated for the implementation of a medical instrument. Issues of prediction and interpretation relative to exercise testing are discussed.