An electromagnetic ventilation monitor was used to record the separate anterior-posterior movements of the chest and abdomen during the breathing cycle in 30 patients with chronic obstructive pulmonary disease (COPD) and in 10 normal subjects. In all normal subjects and 17 COPD patients, the chest and abdomen movements were syndhronous and in phase with the flow of air as measured with a spirometer. In 13 COPD patients chest movement was synchronous with the flow of air, but the abdomen moved inward suddently near or at end inspiration and then outward during a variable part of expiration. Compared to COPD patients with a normal breathing pattern, those with asynchronous breathing movements had poorer ventilatory mechanics and 10 of the 13 were dependent on assisted ventilation. Nine of the 13 patients with asynchronous breathing have died in a 10 month period, a significantly higher mortality than in those with normal breathing.