The proinflammatory cytokine, interleukin-6 (IL-6), seems to be involved in the pathogenesis and progression of IgA nephropathy. Moreover, the transcriptional activity of the IL-6 gene and the plasma levels of IL-6 protein are associated with a single G/C base exchange polymorphism at position -174 of the IL-6 gene promoter. Using PCR-RFLP and PCR product sequencing, we examined the -174 polymorphism in 104 IgA nephropathy patients and in 53 of the normal Korean population. Only 2 GC heterozygous variants and no CC homozygous variants were found (C allele frequency=0.006). These results suggest that the frequency of the C allele in the Korean population is considerably lower than in the Caucasian population, and it appears that the -174 G to C polymorphism of IL-6 is very rare in Eastern Asians. And, the IL-6 polymorphism at -174 is unlikely to contribute significantly to susceptibility to or the progression of IgA nephropathy in Koreans.