Field methods for the measurement of maximum inspiratory and expiratory pressure and for timed and untimed vital capacity have been evaluated critically by repeated use over a 3-month period on a group of 10 cardiorespiratory cripples confined to their homes. Pulmonary pressure measurements can be seriously compromised by use of the cheek muscles. This is avoided by a small hole in the distal end of the mouthpiece, but the test is then influenced by changes in airway resistance. In fit subjects, the recorded pressures depend more on motivation and ability to withstand unpleasant symptoms than on muscular power. The variability of the data and an uncertain theoretical basis make the test of limited value. The vital capacity is accurately measured by the portable bellows spirometer and dynamic properties compare favorably with water-filled systems. Submitted on January 15, 1958