Five hundred twenty-eight pulmonary artery catheters were inserted in 500 patients at the New York University Medical Center between May and November, 1981. Complications occurred in 126 of 528 catheterizations. Serious complications occurred in only 23 of these 528 catheterizations (4.4 percent). These complications, while serious, did not contribute directly to any of 31 deaths seen in these patients. Pulmonary artery catheters were reported by clinicians to have been of benefit in the management of 80 percent of these patients. We conclude, in view of this experience, that the wide use of these catheters is justified, but only if there is a probability that the catheters will significantly contribute to the management of the individual patient.