The use of lipid-lowering drugs has been shown to have beneficial effects in primary and secondary prevention of cardiovascular disease. Gemfibrozil has shown beneficial effects as a lipid lowering agent; however, some proactivating effects on platelet function in vitro have been described. We have studied in a porcine model of atherosclerosis if gemfibrozil could prevent the early vascular effects of a cholesterol-rich diet without inducing platelet activation and, hence, mural thrombosis. Pigs were fed for 50 days with a diet rich in saturated fat and cholesterol (cho). The longitudinal follow-up study showed that in control animals LDL-cho increased significantly up to 181.9 +/- 34.2 mg/dl or 79% of total-cho, while HDL-cho was reduced to 19% of total-cho. Gemfibrozil, at average therapeutic plasma levels (peak levels of 28 micrograms/ml) [corrected], induced a significant reduction in the relative amount of LDL (P < 0.05) and increased HDL (P < 0.05). The increase in fibrinogen plasma levels observed in the control group due to the dietary intervention (+25%) was prevented in the treated animals (-5%). In treated animals, vascular lesions were significantly less severe, platelet deposition upon exposure of damaged vessel wall was unchanged and the fibrin layer deposited on the damaged vessel wall was significantly reduced over control animal values. This short term pharmacologic lipid lowering intervention has been able to slow down lesion development and to reduce fibrin formation onto lesioned disrupted vascular substrates without increasing platelet mural thrombosis.