Elevated serum or plasma Transforming Growth Factor-beta1 (TGF-beta1) {levels have been} linked to cancer and other diseases in numerous studies; however, very few studies have reported an association between circulating TGF-beta1 and lifestyle factors in healthy people. We examined the association between serum TGF-beta1 levels and gender, age, body mass index (BMI), smoking, and drinking in a large population-based cohort study (N =9,142). Serum TGF-beta1 levels were {detected by the Quantikine enzyme-linked immunoassay kit (R&D Systems). The data indicated highly significant (p< ;0.0001) difference in serum TGF-beta1 levels between men (mean value: 37.6 +/- 0.12 ng/mL, N=4888) and women (mean value: 35.1 +/- 0.12 ng/ml, N=4254)}. Serum TGF-beta1 levels decreased with age (trend p< 0.0001) and were positively associated with obesity (trend p< 0.0001) in both men and women. We observed a significant trend with increased serum TGF-beta1 levels corresponding to increased amount of tobacco and alcohol consumption in men (trend p< 0.0001). These findings suggest that serum TGF-beta1 levels appear to be modulated by {gender}, age and lifestyle factors such as obesity, cigarette smoking, and alcohol drinking in healthy Japanese adults.