The gene for glyoxalase I (E.C. 4.4.1.5), Glo, has two alleles, Glo1 and Glo2, which are autosomally inherited in a co-dominant manner. Glo1 allele-frequency is highest in native Alaskan-Eskimo and Indian populations and decreases geographically south and east, to minimum levels in Aboriginal-Australian populations and native tribes in Papua New Guinea. There was no correlation between Glo1 frequency and incidence of insulin-dependent diabetes mellitus (IDDM). The frequencies of GLO phenotypes, Glo 1-1, Glo 1-2 and Glo 2-2, are disturbed in IDDM and there is a suggestion that IDDM patients with or without chronic, clinical complications have characteristic phenotype frequencies.