Eighty-eight patients with insulin-dependent diabetes mellitus (IDDM) and seventy-two unrelated normal controls in Korea were studied for Gm allotypes and HLA-antigens. Ten Gm phenotypes were found among the Korean population. The phenotype frequencies of Gm axg (1,2,21), Gm ag (1,21), Gm agb0b3b5st (1,21, 11,13,10,15,16) and Gm agfb0b1b3b4b5 (1,21,3,11,5,13,14,10) were higher than the other Gm allotypes, but there was no significant difference between patients and controls. HLA-BW54 was found in 15% of patients who had any of those Gm allotypes (Gm axg, Gm agb0b3b5st, Gm ab0b3b5st). However there was no significant difference in frequency as compared with controls.