The human immunoglobulin kappa light chain (IgK) gene is located on chromosome 2p12 and consists of a single constant gene (Ck), five joining genes (Jk) and a number of variable genes (Vk). Three alleles for Ck have been defined by serological assay or PCR-ASO method. These alleles involve single amino acid changes at positions 153 and 191. The allotypes of the Kappa constant region were designated as follows : Km¹ has valine (GTC) at position 153 and leucine (CTC) at 191 : Km¹,² has Ala^(153) (GCC) and Leu^(191) (CTC): Km³ has Ala^(153) (GCC) and Val^(191) (GTC). This study used the PCR-ASO to provide specific allelic typing system for Km at the IgK gene. The Km was typed in 131 normal Korean. For Km genotyping, 354 by sequence was amplified by primers (BA05 5` ACT GTG GCT GCA CCA TCT G 3` and BA06 5` GAA CTG AGG AGC AGG TGG G 3`). Amplified gene was hybridized with Km ASO probes and detected using colorimetric detection method. The frequencies of Km genotypes Km³, Km³:¹,² and Km¹,² were 35.1%, 45.1% and 19.8%, respectively. The estimated allele frequencies for Km³ and Km¹,² were 0.58 and 0.42, respectively. The Km³ frequencies were in the range of 0.9 in the caucasoid populations (Europeans, Polish Jews) and close to 0.5 in the mongoloid (Chinese, Japenese, Melanesians) and African (Zaire Pygmies).