&NA;We evaluated the ability of intermittent external pneumatic calf compression to prevent deep venous thrombosis after subarachnoid hemorrhage from ruptured intracranical aneurysms. Fifty‐six subarachnoid hemorrhage patients not given external pneumatic calf compression were compared with 90 patients who had calf compression after their subarachnoid hemorrhages. Both groups of patients were on strict bedrest for 7 to 21 days after aneurysm rupture, and both received e‐aminocaproic acid, 30 to 36 g/day intravenously, until operation. The risk factors in the two groups were similar, and the nursing and medical care did not seem to differ. Of patients without external pneumatic compression, 18% had venographically proven deep venous thrombi, which contrasts with 6% of patients receiving calf compression. This was a significant difference (p< 0.05; x2). These retrospective data suggest that external pneumatic calf compression helps to prevent deep venous thrombosis in patients with subarachnoid hemorrhage when delayed operation, bedrest, and antifibrinolytic agents are used. (Neurosurgery18:25‐28, 1986)