We investigated the effects of smoking cessation or alcohol restriction on metabolic and fibrinolytic variables in Japanese men. In the smoking study, 35 male subjects [32+/-1 (S.E.M.) years] who habitually smoked cigarettes (29+/-3 cigarettes/day) were told either to keep their usual smoking habits for 1 week, or to abstain from cigarette smoking, using a randomized crossover design. In the alcohol study, 33 male subjects (37+/-1 years) who habitually drank alcohol (64+/-6 ml of ethanol/day) were told either to keep their usual drinking habits for 3 weeks, or to reduce alcohol intake by at least up to a half of their usual drinking amount, using a randomized crossover design. In each study, venous blood samples were drawn after a 12-h overnight fast on the last day of each period, and metabolic and fibrinolytic variables were measured. One-week smoking cessation significantly increased serum high-density lipoprotein (HDL) cholesterol levels (P<0.05), and significantly decreased serum lipoprotein (a) levels (P<0.01) and plasma plasminogen activator inhibitor-1 levels (P<0.05). In contrast, 3-week alcohol restriction significantly decreased serum HDL cholesterol levels (P<0.05) and plasma tissue plasminogen activator levels (P<0.05). These results suggest that smoking cessation has substantial and immediate benefits on lipid and fibrinolytic variables in habitual smokers, whereas alcohol restriction increases cardiovascular risks, in some respects, in habitual drinkers.