Intermittent positive pressure ventilation (IPPB) is reported to improve lung compliance and decrease the work of breathing in subjects with kyphoscoliosis. These results suggest that IPPB may improve chest wall and lung compliance in patients with neuromuscular disease. We studied the short-term effects of IPPB on total respiratory system compliance in 14 subjects with neuromuscular disease. Seven were quadriplegics, and seven had muscular dystrophy. Vital capacity was reduced to 38 +/- 14 percent of the predicted normal values. Baseline measurements of total respiratory system compliance were 57 +/- 18 percent when compared to normal control values. After a 20 minute treatment of IPPB delivered with inspiratory pressures of 20 to 25 cm H2O that more than tripled resting tidal volume, there was no significant change in total respiratory system compliance in either group of patients. These findings indicate that patients with quadriplegia or muscular dystrophy do not derive immediate improvement in ventilatory mechanics from IPPB treatments.