Pulmonary artery thromboendarterectomy (PAT) is a potentially curative procedure in chronic, major vessel thromboembolic pulmonary hypertension. However, postoperative reperfusion pulmonary edema (RPE) has been a serious complication, often requiring prolonged mechanical ventilation. This entity has been described only anecdotally in the past. To characterize it more fully, we retrospectively analyzed the course and potential determinants of RPE after thromboendarterectomy in 22 patients who had PAT at our institution from 1969 through 1984. Particular attention was directed to clinical data, thrombus location, areas operated, postoperative roentgenograms, and preoperative and postoperative hemodynamic data. In all patients but 1, RPE developed within 72 h after surgery, corresponding to anatomic locations distal to vessels subjected to PAT. Regions of lung not reperfused at surgery were uniformly spared. Pulmonary capillary wedge and/or left atrial pressures preoperatively and postoperatively were not elevated. None of the preoperative data predicted which patients would develop more persistent RPE. These observations suggest that the phenomenon of RPE is a peculiar, focal form of pulmonary edema, the basis for which remains to be defined.