For many years, it has been known that genes and environmental factors interact to determine an individual's blood pressure. The purpose of this article is twofold. First, the authors review current molecular genetic approaches to delineating genes that lead to the development of hypertension, focussing on the renin-angiotensin system. We then consider perinatal environmental factors that impact adult blood pressure. Epidemiologic data suggest that good maternal nutritional status is essential to avoid programming individuals for future health problems as adults. One factor that appears to play an important role in programming for hypertension in adulthood is maternal dietary protein restriction during pregnancy, possibly by suppression of the fetal renin-angiotensin system and consequent impairment of renal development. The association between lower birthweight and increased adult blood pressure, established in epidemiologic studies, may be caused by suboptimal maternal diet or placental insufficiency, resulting in transient changes in fetal hormone systems or gene expression that permanently alter the structure and function of the kidney and vasculature.