Backgroend: The incidence of IDDM in Oriental in- cluding Korean is 1/J.0-1/20 of the Caucacian. Recently, some investigators explain the racial difference of cilnical characteristics and incidence with the difference of the susceptibility genes and or with their frequency in the general population of that race. Methods: To identify the susceptibility genes in the development of IDDM among Korean aduIts, the genotyping of HLA DQA1, DQB1 alleles was performed for 28 adult IDDM patients, and 38 normal controls using the sequence specific oligonucleotide probes. Results: The frequncy of HLA DQA1 '0301 allele is increased in the Korean adult IDDM patients comparing with normal controls, but the frequency of HLA DQB1' 0302, 0201 alleles, which are well-known susceptibility genes in the development of IDDM in Caucacian subjects were not increased. Conclusion: These resuits suggest that one of the susceptibility genes in the development of IDDM among Korean adults is HLA DQA1 0301 allele,