This report reviews our experience with external pneumatic compression (EPC) therapy in preventing clinically evident deep venous thrombosis (DVT) and pulmonary emboli (PE) in neurological and neurosurgical patients. A total of 523 patients admitted to the Departments of Neurology and Neurosurgery at the Massachusetts General Hospital from December 1980 through January 1984 are included. The incidence of DVT despite EPC use was 2.3%. The incidence of PE diagnosed by lung scan and usually confirmed by angiography was 1.8%. In conjunction with previously published reports of the incidence of DVT and PE, these data suggest that EPC may be efficacious in decreasing the incidence of DVT but may not prevent PE in neurological and neurosurgical patients.