Impaired fibrinolysis due to high plasminogen activator inhibitor levels is present in patients with a variety of thrombotic diseases. Plasminogen activator inhibitor levels correlate with triglyceride levels and are elevated in patients with hypertriglyceridemia. Treatment of asymptomatic hypertriglyceridemic patients with diet or medication results in improvement of fibrinolytic parameters. To determine if similar improvements in fibrinolysis occur during treatment of hypertriglyceridemia in patients with a history of venous thrombosis and impaired fibrinolysis due to high plasminogen activator inhibitor levels, 5 patients were given gemfibrozil. Triglyceride levels and fibrinolytic response to venous occlusion were determined before and after 30 days of treatment. Gemfibrozil therapy resulted in a predictable decrease in triglyceride levels in all patients, a reduction that was statistically significant (p = 0.04). There was no significant change in fibrinolytic variables during gemfibrozil therapy. Independent factors appear to control the plasminogen activator inhibitor and triglyceride levels in patients with a history of venous thrombosis.