Little information is available concerning the effect of pneumatic antishock trousers (PT) on pulmonary function. To examine this issue, we measured the effects of PT inflation on forced expired volumes, subdivisions of lung volumes, quasistatic lung compliance, single-breath diffusing capacity for carbon monoxide, and transdiaphragmatic pressure at resting lung volume in 10 healthy nonsmoking adults. All subjects were studied seated without PT, supine with PT uninflated, and supine with PT inflated to 100 mm Hg. When seated subjects assumed the supine position without PT inflation, significant reductions were found in the forced expired volume in 1 sec, in subdivisions of lung volume, total lung capacity (TLC), functional residual capacity (FRC), expiratory reserve volume (ERV) and in transdiaphragmatic pressure. However, PT inflation itself did not produce significant changes in any of the measured pulmonary indices except transdiaphragmatic pressure. We conclude that PT inflation in supine normovolemic individuals does not produce acutely significant alterations in lung function.