The HLA-DRB1*15 allele, which, despite a frequency of 0.14 in African American control subjects that is consistent with Europeans (see also Supporting Information, Table S1), was more common than expected in our African American case subjects: 0.06 compared with ≤ 0.01 in European subjects with Type 1 diabetes. This evidence concerns the gene HLA-DRB1 and type 1 diabetes mellitus.