We have studied the relationship between the DNA polymorphisms and the development of diabetes in Caucasians and US black populations. The analyses suggest that disease susceptibility differs in the two populations. In a large population with low frequency of diabetes, DNA fragments detected in the studies of the human insulin gene and HLA-DR regions seem to have a minor role in the development of diabetes. However, the currently available data also show that alleles with insertion in the 5'-flanking region of the insulin gene in the US black populations induce noninsulin-dependent diabetes fivefold more often than in white populations. To draw a more reliable conclusion, further DNA polymorphism surveys in different ethnic groups need to be conducted.