Genetic susceptibility to common diseases is likely influenced by common DNA variants with small-to-moderate effects, rather than by rare mutations with large effects. The majority of such common variation occurs in the form of single nucleotide polymorphisms (SNPs). DNA sequence variation, including SNPs, is created and maintained by the action of evolutionary forces such as mutation, recombination, and selection. Over time and space, these forces have shaped the relationships between the contemporary organization of the human genome and disease susceptibility in the population at large. Single nucleotide polymorphisms have emerged as valuable new tools to uncover these relationships. In particular, their use in both genome-wide and gene-based association studies holds great promise for the identification of genes and gene variations involved in predisposition to essential hypertension. New advances in biotechnology are making possible large-scale discovery of SNP variation and rapid application of this information to disease gene discovery.