Recent reports indicated that high levels of interleukin 10 (IL-10) contribute to the monocytes paralysis and poor clinical outcome in acute liver failure (ALF). Polymorphisms in the promoter region of IL-10 affect IL-10 production and confer susceptibility to inflammatory diseases. The aim of this study was to determine the possible association of the three polymorphisms (A-1082G, T-819C, A-592C) in the IL-10 gene promoter with the susceptibility to hepatitis B virus (HBV)-related ALF in a Chinese population. The IL-10 gene promoter polymorphisms were genotyped in 414 unrelated healthy blood donors, 367 asymptomatic HBV carriers and 345 HBV-related ALF patients. Functional analyses were conducted to verify the biological significances of the associated genetic variations. The allele frequencies of IL-10-592C and -819C were significantly higher in HBV-related ALF patients than in blood donors and asymptomatic HBV carriers. Logistic regression analysis and stratification analysis with adjustment for age and sex indicated that the polymorphisms of A-592C and T-819C were associated with susceptibility to HBV-related ALF (P = 6.9 x 10(-7)), and the -1082A-819C-592C haplotype in the IL-10 gene promoter were associated with an increased susceptibility to ALF in HBV carriers (dominant model, P = 0.0002, odds ratio = 1.60, 95% CI 1.25-2.07). Functional analyses showed that the A-592C polymorphism is a nuclear proteins binding site, and the disease susceptible -592C allele had a higher transcription activity compared with -592A allele. This study emphasizes the importance of IL-10 in the pathophysiology of HBV-related ALF on the population level.