The high affinity receptor for sulphonylureas, expressed on the beta cells of the pancreas, plays a crucial role in the control of insulin secretion. Mutations in the cytoplasmic domain of the sulphonylurea receptor (SUR) gene that disrupt the regulation of insulin secretion have been previously described. In the present study, the potential role of genetic variation in the SUR gene has been investigated in non-insulin-dependent diabetes mellitus (NIDDM) through linkage studies with microsatellite markers tightly linked to the SUR gene. The microsatellite markers were typed in 346 Mexican-American NIDDM affected sib pairs derived from 176 families and an additional 110 ethnically and geographically matched control subjects. No evidence of linkage, based on allele sharing, or association based on allele frequencies in patients and control subjects, for any microsatellite marker and NIDDM was observed in this population. These results suggest that genetic variation in the SUR gene does not play a major role in susceptibility to NIDDM in the Mexican-American population.