Renin alleles in the Dahl salt-hypertension sensitive (S) and Dahl salt-hypertension resistant (R) rats are known to strongly cosegregate with blood pressure. The purpose of this work was to look for structural differences in the S and R renin alleles that could account for the cosegregation result. The nucleotide sequences determined for the coding region and the 5'-flanking regulatory region for the renin gene of S and R rats were identical. There were some minor nucleotide changes in selected regions of the 1st and 8th introns that were sequenced, but these were unlikely to be of functional importance. The remaining possible reasons for the cosegregation of blood pressure with renin alleles in Dahl rats are differences in renin regulatory elements out of the immediate 5'-flanking area, or differences in alleles at an unknown closely linked locus.