Between 1978 and 1985, 88 patients underwent insertion of the Greenfield vena cava filter. In 21 of the 88 patients (23.9%) the filter was inserted prophylactically. Sixteen of the 21 prophylactic insertions were performed before total joint replacement in patients with a history of venous thromboembolism. Operative morbidity (4.6%) was minor and occurred only early in the series. The operative mortality rate was 4.6%. None of the deaths were related to filter insertion or pulmonary embolism. Follow-up in 65 patients (73.9%) ranged from 1 to 60 months (mean, 16.4 months). Leg edema developed in 9.2% (6/65), stasis ulceration in 3.1% (2/65), caval occlusion in 7.5% (3/40), and recurrent nonfatal embolism in 3.1% (2/65) of the patients. In the patients who received prophylactic filters before total joint replacement, there were no filter-related complications or episodes of pulmonary embolism. This series confirms the safety and effectiveness of the Greenfield filter and suggests that the indications for its use might be liberalized to include prophylactic insertion of the device in certain high-risk patients.