Preeclampsia (PE) is one of the most serious disorders of human pregnancy and Th1/Th2 imbalance may play a role in its etiology. Considering that cytokine production is under genetic control, in this study we have investigated IFN-gamma+874 (T/A) and three bi-allelic IL-10 promoter polymorphisms in a total of 134 preeclamptic women compared to 164 healthy women. It was shown that the IL-10 -1082 G allele frequency increases significantly in patients compared to the control group (P=0.045). No significant differences were found in any other genotype or allele frequencies of IL-10 and IFN-gamma genes between the two groups. In addition, the frequencies of three common IL-10 haplotypes (GCC, ACC, ATA) did not show any significant difference between the study groups. Since the presence of G nucleotide at position -1082 of IL-10 gene is associated with reduced cytokine production, therefore, the higher frequency of IL-10 -1082 G allele in preeclamptic patients compared to controls may be considered as a genetic susceptibility factor for the development of PE.