Renal failure is a well-recognized complication of accelerated and malignant hypertension that can be prevented by appropriate antihypertensive therapy. The risk of renal disease in patients with milder forms of hypertension is less certain. Death certificate, insurance industry, and community-based observational studies provide little information with respect to the risk of kidney damage in the hypertensive patient. Randomized controlled trials of antihypertensive drug therapy provide equivocal results. The strongest evidence in support of the hypothesis that mild hypertension increases the risk of subsequent renal disease comes from analyses of the Hypertension Detection and Follow-up Program and the Medicare End-Stage Renal Disease (ESRD) Program. The risk of blood pressure-related ESRD appears to be especially high in blacks, independent of age, sex, and prevalence of hypertension. Although these results need to be confirmed, the data raise the possibility that the effects of high blood pressure on the kidney are different in blacks than in whites. Based on current trends, it is projected that the number of beneficiaries in the Medicare ESRD Program will continue to increase during the next 30-40 years and that the diagnosis of hypertensive ESRD will become increasingly common. Additional studies to characterize the relation between mild hypertension and subsequent risk of renal disease and to confirm the corresponding benefits of antihypertensive therapy are urgently needed.