Blacks in the United States have a much greater prevalence of essential hypertension than whites. The prevalence of hypertension for adults aged 18-74 has been estimated at 15.7 percent for white women, 18.5 percent for white men, 27.8 percent for Black men and 28.6 percent for Black women. Among adults who underwent screening for the Hypertension Detection and Follow-up Program, 36.2 percent of Black males and 38.2 percent of Black females either had diastolic blood pressures at least as high as 95 mmHg or were taking antihypertensive medications. The Black-white ratio for the prevalence of hypertension in this survey was approximately 2. Reportedly, the prevalence of hypertension among inner city Blacks may be as high as 50 percent. The exact causes of the disparity in hypertension prevalence between Blacks and whites are unknown, but genetic predisposition, psychosocial stress, and life-style factors such as high sodium ingestion and obesity have been implicated. None of these factors alone appears sufficient to account for the difference in the prevalence of hypertension between Blacks and whites, suggesting that multiple factors and/or interactions between factors may be involved.