The overall goal of this study is to identify genes that interact with the environment to influence cardiovascular disease risk. To do so, we are performing 4 short-term interventions known to influence variation in risk factors (e.g., blood pressure) for cardiovascular disease (CVD). Our hypothesis is that the effect of some genes may be restricted to a particular environment (e.g., pre- or post-intervention) while other genes may influence trait variation in response to the intervention. Our primary phenotype of interest is blood pressure response to changes in sodium intake (or salt sensitivity, a significant predictor of all-cause and CVD-related mortality). Our strategy, which takes advantage of recent, technological advances in high-throughput genotyping of single nucleotide polymorphisms (SNPs) across the genome, utilizes linkage and linkage disequilibrium mapping methods to identify regions of the genome linked to or associated with variation in blood pressure response.