To test the hypothesis that race is a predictor of hypertensive renal disease, we examined a general medicine clinic population of 6,880 hypertensive patients who were treated for at least 1 year (mean, 5.2 years). Their mean age was 55.8 years; 70% were women, 72% were black, and 41% were diabetic (95% type II). Many were already under treatment at the time of enrollment. Their mean blood pressure at entry was 150/92 mmHg; during treatment it was 142/86 mmHg. Decreased renal function, defined as a serum creatinine greater than or equal to 2 mg/dL, developed in 18.1%. A multivariable logistic regression analysis identified diabetes, glucose control, systolic blood pressure levels, heart failure, and male gender as indicators of decreased renal function. These data suggested that glucose and blood pressure control may decrease the frequency of impaired renal function. However, when these variables were controlled, blacks still had almost twice the risk for renal dysfunction (91% greater risk) than whites (P less than 0.0001). With increasing creatinine values, the percentage of black patients increased progressively. The data draw attention to and elucidate the exceptionally high incidence of renal dysfunction in blacks with or without diabetes. Further, they may explain the inordinate numbers of blacks with hypertension requiring dialysis. Finally, these retrospective data suggest that prospective trials to test the effect of blood pressure and glucose control on the course of renal disease in hypertensive and/or type II diabetic patients are warranted.