BACKGROUND AND PURPOSE: Conflicting findings on the possible association between hepatitis B virus surface antigen (HBsAg) seropositivity and atherosclerosis have been reported. We examined the association between HBsAg seropositivity and cardiovascular diseases in a cohort of Koreans with a high prevalence of hepatitis B viral infection. METHODS: Men (N=521 421) aged 30 to 64 years were categorized into 4 groups according to HBsAg seropositivity status and the presence of liver dysfunction were followed up from 1990 to 2001 for both fatal and nonfatal myocardial infarctions (MIs) and strokes. The associations of HBsAg seropositivity with these cardiovascular diseases were examined with a Cox proportional-hazards model. RESULT: Overall, HBsAg seropositivity was associated with a decreased risk of ischemic stroke and MI and an increased risk of hemorrhagic stroke, with multivariable-adjusted hazard ratios (95% CIs) of 0.79 (0.68, 0.90), 0.74 (0.62, 0.87), and 1.33 (1.15, 1.52), respectively. Risks for stroke and MI were similar between HBsAg-seronegative and HBsAg-seropositive men in the absence of liver dysfunction, whereas men with both HBsAg seropositivity and liver dysfunction had a higher risk of hemorrhagic stroke and lower risks of ischemic stroke and MI compared with HBsAg-seronegative men. CONCLUSIONS: The association between HBsAg seropositivity and stroke and MI appears to be secondary to the liver dysfunction associated with hepatitis B viral infection. HBsAg seropositivity itself did not appear to play an important role in atherothrombosis through inducing a proinflammatory effect.