In a randomized five-year multifactorial primary prevention trial of vascular diseases, hyperlipidemias, hypertension, smoking, obesity, and abnormal glucose tolerance of the high-risk test group (n=612 men) were treated with dietetic-hygienic measures and hypolipidemic (mainly probucol and clofibrate) and antihypertensive (mainly diuretics and β-blockers) agents. A matched high-risk control group (n=610) and a low-risk control group (n=593) were not treated. The program markedly improved the risk factor status, yet the five-year coronary incidence tended to be higher in the intervention group than in the control group (3.1% vs 1.5%), while the stroke incidence was significantly reduced (1.3% vs 0%). The coronary events tended to be accumulated in subgroups treated with β-blocking agents or clofibrate, but there were few in those receiving probucol or diuretics. Thus, the intervention program significantly reduced development of stroke, but the occurrence of cardiac events was not prevented. Possible adverse drug effects offsetting the probable benefit of improved risk profile are not excluded.