SummaryGenetic polymorphisms of the complement components C6 and C7 were investigated in Korean living in Seoul using isoelectric focusing and immunoblotting. Three common and four rare C6 allotypes were observed. The allele frequencies estimated were as follows: C6*A 0.433, C6*B 0.523, C6"B2 0.039, and rare alleles (M91, M92, M11 and M2) 0.005. Three C7 variants, besides a common allele, were observed with polymorphic frequencies. Two rare C7 variants, considered to be new, were also observed. The allele frequencies estimated for C7"1, C7"2, C7"3, C7"4, and rare variants (tentatively named K1 and K2) were 0.843, 0.073, 0.034, 0.048 and 0.002, respectively. The C6 and C7 allele frequencies are similar to those in Japanese and Chinese. The association analysis between C6 and C7 showed a significant negative association between C6 B and C7 4 allotypes (p < 0.02).