Automatic flow interruption technique has been utilized for the determination of lung and thorax compliance. The rate of interruption has been fixed at 120 min-1 with a closingtime of 0.36sec. The short interruption time does not create discomfort for the patientand allow very little time to the patient to activate his respiratory muscle or to close his glottis during stopping the flow. Compliance values, from 31 subjects of various health status, obtained by this technique as well as by slow inspiration technique agree well.