The purpose of the present paper was to report genetic constitution of genetic variants o1 serum prealbumin(Pr) locus in Korean racing horse populaltion by starch gel electrophoresis. The results obtained from this study were summarized as follows: 1. The prealbumin locus was controlled by four codominant autosomal multiple alleles, designated Pr^F, Pr^I, Pr^L and Pr^S. 2. The prealbumins were classified into nine phenotypes, FF, FL, FS, II, IL, IS, LL, LS and SS. However, the heterozygous phenotype FI was not observed. In the distribution of phenotypes, Pr LL type was the most common allele(66.42%). Secondarily, Pr II type was 13.87%, and all the other types were less than 5 %. 3. The frequencies of the Pr^L, Pr^I, Pr^F and Pr^S alleles were 0.726. 0.157, 0.044 and 0.073. respectively. Therefore, gene frequency of Pr^L allele was highly predominant.