As a part of the investigation for clarifying the genetic composition of Korean population, phenotypes and allele frequencies of complement Factor I and complement Factor H in the blood were analysed by polyarcrylamide gel isoelectric focusing followed by immunoblotting. Blood samples were obtained from healthy individuals living in Seoul, Kangreung and Cheju, Korea. Three phenotypes of complement Factor I (FI A, FI AB and FI B) appeared in Korean population. The allele frequencies of FI*A and FI*B were 0.9011 and 0.0989, respectively. Phenotypes of complement Factor H were classified into three common types (FH A, FH AB and FH B) and five rare types (FH A1, FH A1A, FH A1B, FH BM and FH QO). Allele frequency of Mongoloids was lower than that of Caucasoid populations. The FH*B frequency appeared relatively higher than FH*A frequency in most populations studied. Rare alleles, FH*M and FH*QO, appeared in Korean and Japanese populations.