To assess the association of polymorphisms at the sulphonylurea receptor (SUR1) gene with the development of Type 2 diabetes mellitus, 456 subjects, 236 with Type 2 diabetes and 220 non-diabetic controls, were analysed for variants at exon 7, exon 22 and intron 24 of the SUR1 gene by the polymerase chain reaction and restriction fragment length polymorphism. The T761T substitution in exon 22 of the SUR1 gene was not found in either diabetic patients or non-diabetic controls. Both the exon 7 variant and the intron 24 variant were present in both groups at similar frequencies. No significant association was seen between either variant and obesity. Diabetic patients homozygous for the -3C allele of intron 24 had a higher ratio of positive family history than patients homozygous for the -3T allele (p = 0.03). We conclude that these polymorphisms are not major determinants of diabetes and obesity in the Japanese population.