Immunological abnormalities have been found to be associated with schizophrenia for decades. Cytokines are key proteins involved in the immune system activation. Interleukin-10 (IL-10), an important immunoregulatory cytokine, is located on chromosome 1q31-32, a region previously reported to be linked to schizophrenia in genetic studies. Thus, a study was carried out on the association between schizophrenia and three single nucleotide polymorphisms in the promoter region of IL-10 gene. Totally, 341 patients and 334 controls of Chinese descent were analyzed. Statistically significant differences were observed in both allelic and genotypic frequencies of the -592A/C polymorphism (Allele, chi(2)=4.43, df=1, P=0.032, odds ratio (OR)=1.26, 95% CI 1.02-1.56; Genotype, chi(2)=6.18, df=2, P=0.044) while the other two polymorphisms did not show such differences. The observed haplotype distributions revealed a significant association with schizophrenia (P=0.0008). These data suggest that the IL-10 gene may confer susceptibility to the development of schizophrenia in the Chinese population.