High body mass index (BMI) is considered as the most important risk factor for elevated serum alanine aminotransferase (ALT) concentration. This study examined an array of factors, including waist circumference (WC) and folate deficiency, which may mediate the association of BMI with serum ALT concentration in Chinese hypertensive adults without known hepatic diseases. A multicenter, cross-sectional study was carried out. A total of 378 patients with mild or moderate hypertension and without known hepatic diseases were recruited from five hospitals in Harbin, Shanghai, Beijing, Xi'an, and Nanjing. Of the 360 hypertensive patients with complete data in our final analysis, 13.6% had high ALT concentrations (> 40 IU/L). Factors including BMI, WC, triglyceride level, and folate concentration were associated with ALT concentration in univariate analysis. Consistently higher prevalence rates of elevated ALT were observed in subjects with lower folate concentrations (a parts per thousand yen12 vs. < 12 nmol/L, 9.9% vs. 17.8%, P=0.03), with higher BMI (a parts per thousand yen28 vs. < 28 kg/m(2), 21.5% vs. 11.4%, P=0.02) or higher WC (a parts per thousand yen90 vs. < 90 cm, 18.5% vs. 10.0%, P=0.02). However, in multivariate analysis, the association between BMI and ALT concentration disappeared (P=0.802 in males and 0.369 in females), while WC in females (P < 0.001) and folate concentration (P=0.036 in males and 0.044 in females) remained as significant predictors for ALT concentration. This multicenter study demonstrated that WC and low folate concentration were important factors underlying the association between BMI and ALT concentrations in Chinese hypertensive adults without known hepatic diseases.