This study evaluated whether hypertensive siblings had excess sharing of RsaI and SstI alleles of the insulin receptor gene compared with a random population. Thirty families consisting of 60 affected individuals with established hypertension were genotyped for the RsaI and SstI restriction fragment length polymorphisms and the resulting genotype data was analysed using the affected pedigree member method of linkage analysis. The hypertensive siblings were found to have increased sharing of INSR alleles; however, this linkage could not be confirmed using a maximum LOD score method. Thus, the results from this study do not support a role for the INSR gene in the genesis of essential hypertension in the population studied.