This community-based study in three geographically distinct populations of West African heritage with contrasting levels of hypertension risk was one of the first comprehensive examinations of the genetics of hypertension in African Americans. The study focused on the renin-angiotensin system (RAS) because it was the only physiological arm of blood pressure control for which candidate genes had been securely linked to the risk of hypertension. Polymorphisms at the angiotensinogen locus varied considerably between Blacks and whites. The documented Black:white differences in the RAS system emphasized the importance of determining whether RAS genes contributed to the excessively high risk of hypertension experienced by African Americans. The study generated unique information about the variability of the RAS loci in populations of West African heritage, and the contribution of this variability to hypertension risk. The data from the study, including the DNA specimens, also represented a valuable resource for future work on the genetics of hypertension in this important ethnic group.