Polymorphisms of six red cell enzymes were studied on unrelated individuals from three areas (Seoul, Kangreung and Cheju) of Korea by horizontal starch gel electrophoresis. There were two G-6PD alleles, GdB+ and GdB-, in Korean populations. The allele frequencies of GdB+ in males were 0.9723 in Seoul, 0.9689 in Kangreung and 0.9726 in Cheju. Three soluble GOT alleles, GOTS1, GOTS2 and GOTs3 , were found in Korean populations. The allele frequencies of GOTS1 were 0.9832 in Seoul, 0.9852 in Kangreung and 0.9851 in Cheju. It was interesting to note that GOTs3 allele was detected in Korean populations. The frequencies of GOTs3 were 0.0049 in Seoul and Kangreung, and 0.030 in Cheju. In esterase D study, two common alleles, EsD1 and EsD2 were found. Allele frequencies of EsD1 were 0.6702 in Seoul, 0.6640 in Kangreung and 0.6716 in Cheju. There were two common acid phosphatase alleles, AcPa and AcPb, in Korean population. AcPc allele which was common in Caucasoids and rare alleles were not found. the allele frequencies of AcPs were 0.3930 in Seoul, 0.4071 in Kangreung and 0.3826 in Cheju. In LDH and MDH studies, only the normal phenotype and no variant type were found. No variant type was found in both enzyme systems. So, LDH and cytoplasmic MDH seem to be monomorphic traits in Korean populations. The gene frequencies and polymorphic phenotypes of the above red cell enzymes were discussed in comparison with the other populations.