The characteristics of allelic polymorphisms of the two (CA)n microsatellite (p599 and ㅅ599) markers spanning the long arm of chromosome 5 were studied in 52 DNA samples from unrelated inhabitants of Seoul (Korea) by using the polymerase chain reaction (PCR) to investigate differences in allele frequencies between Korean and Caucasian populations. The 6 alleles were observed for p599 (CA)n with a polymorphism informative content (PIC) value of 0.71 and 9 alleles for ㅅ599 (CA)n with a PIC value of 0.82. The observed heterozygote frequencies of the loci were estimated to 0.730 and 0.846, respectively. Several allele frequencies of two loci showed significant differences between Korean and Caucasian populations. Genotype data from the two loci were consistent with the Hardy-Weinberg equilibrium by x2 test. Linkage disequilibrium between p599 (CA)n and ㅅ599 (CA)n loci was observed in x2 test between the observed and expected frequency of allelic association. The probability of matching calculated at each locus was 0.104 for p599 (CA)n and 0.043 for ㅅ599 (CA)n, respectively. These results demonstrate the need to determine populationspecific allele frequency distributions for polymorphic markers when performing genetic linkage studies in racially defined several populations.