The production of transforming growth factor beta 1 (TGF-beta1) has been reported as being significantly associated with the gene polymorphism in the leader sequence at positions +29. The current study aimed to evaluate the associations between the polymorphism and the clinical characteristics of chronic hepatitis C (CHC). A total of 422 (252 men; mean age: 49.7 +/- 11.2 years) Taiwanese CHC patients with liver biopsies were enrolled. The TGF-beta1 gene polymorphism at position +29 (T or C), hepatitis C virus (HCV) RNA genotypes, and serum HCV RNA levels of these patients were determined. Of the 422 patients, the frequency of the T allele was 45.4%. Based on univariate analyses, a significantly lesser proportion of patients with allele T had high viral loads than those who were without allele T (P = 0.026). The lesser HCV RNA levels and HCV genotype 1b infection were significantly associated with the inheritance of the T allele in female patients based on univariate (P = 0.012 and 0.007, respectively) and multivariate regression (odds ratio/95% confidence interval: 0.434/0.219-0.859 and 0.468/0.237-0.927, respectively) analyses. In male patients with or without inheritance of the T allele, the clinical characteristics were similar. In conclusion, the association between TGF-beta1 polymorphism and virologic characteristics of chronic HCV infection implicated a significant role of host genetic factors on the clinical features of CHC. Female patients who carry T allele at position +29 were predisposed to be associated with HCV genotype non-1b infection and lesser HCV viral load, which revealed the gender effect.