Background: Serum total bilirubin (TB) is a potent antioxidant and may be a negative risk factor of cardiovascular disease. In non-diabetic adults, hemoglobin A_1c (HbA_1c), but not fasting plasma glucose, is an independent risk factor of cardiovascular disease. Methods and Results: Linear regression using TB as a dependent variable and cardiovascular risk factors, including HbA_1c, as independent variables, linear regression using HbA_1c as a dependent variable and other cardiovascular risk factors, including TB, as independent variables, and logistic regression using the highest decile (≥5.4%) of HbA_1c as a dependent variable and TB and other cardiovascular risk factors as independent variables were performed for 893 apparently healthy male smokers, 1,607 male nonsmokers, and 1,680 women. The standardized regression coefficient of HbA_1c for TB and that of TB for HbA_1c was -0.12 (P=0.007) and -0.06 (P=0.02), respectively, in the smokers, -0.20 (P<0.0001) and -0.07 (P<0.0001), respectively, in the nonsmokers, and -0.21 (P<0.0001) and -0.14 (P<0.0001), respectively, in the women. The odds ratio of 1 SD increment in TB for HbA_1c ≥5.4% was not significant in the smokers, 0.67 (P=0.002) in the nonsmokers, and 0.55 (P<0.0001) in the women. Conclusions: Bilirubin was negatively associated with HbA_1c independently of other cardiovascular risk factors in apparently healthy Japanese men and women. The association was weak in male smokers. (Circ J 2011; 75: 190-195)