Preeclampsia is a severe complication of pregnancy characterized by an excessive maternal systemic inflammatory response with activation of both the innate and adaptive immune system. Interleukin-10 affects maternal intravascular inflammation, as well as endothelial dysfunction. The aim of the study was to investigate the association between IL-10 T-819 C polymorphism and preeclampsia. A total of 120 pregnant women with preeclampsia and 120 women with normal pregnancy attending the Gynecological Unit of Government Maternity Hospital, Petlaburz, Hyderabad, India, were considered for the present study. A standard amplification refractory mutation system (ARMS) PCR was carried out for genotyping of IL-10 T-819 C promoter polymorphism in all the participants. Genotypic distribution of the control and patient groups was compared with values predicted by the Hardy-Weinberg equilibrium using χ2 test. Odds ratios (OR) and their respective 95 % confidence intervals were used to measure the strength of association between IL-10 gene polymorphism and preeclampsia. The frequencies of IL-10 T-819 C genotypes, CC, CT, and TT, were 47.5, 28.3, and 24.2 % in women with preeclampsia and 20.8, 48.3, and 30.8 % in the controls, respectively. There is a significant difference in the distribution of genotypes and alleles of IL-10 T-819 C between the two groups (test power = 0.66). The present study suggests that the IL-10 T-819 C gene promoter polymorphism can be a major genetic regulator in the etiology of preeclampsia.