In a heterogeneous group of 23 critically ill patients with recurrent and intractable bouts of supraventricular arrhythmia, increases in pulmonary artery wedge pressure significantly decreased cardiac output and exacerbated respiratory failure. Most patients were eventually stabilized on a long-term iv infusion of the calcium antagonist verapamil which, with appropriate monitoring, was well tolerated. We suggest that the use of verapamil infusion may play a significant role in the management of such patients and that further studies are justified.