The long-term effects of converting enzyme inhibitors and calcium channel blockers on proteinuria and the progression of renal disease in patients with hypertension and chronic renal insufficiency are not well established. We have studied the long-term effects of treating hypertension with an angiotensin-converting enzyme inhibitor, enalapril, and a calcium channel blocker, nicardipine, on urinary albumin excretion (UAE) and on renal function in 16 patients with hypertension and chronic renal insufficiency (creatinine clearance ranging between 17 and 62 ml/min). After 1 year of treatment, these agents caused a similar decrease in blood pressure. Only enalapril, however, caused a significant decrease in UAE (from 641 +/- 98 to 292 +/- 47 mg/24 h, p less than 0.01), whereas UAE did not change in the group treated with nicardipine (675 +/- 78 vs. 601 +/- 75 mg/24 h). Creatinine clearance at the beginning of the study was similar in the group treated with enalapril and in the group treated with nicardipine (35 +/- 3.6 vs. 40 +/- 4.1 ml/min). After 1 year of follow-up, creatinine clearance remained unchanged in both groups of patients. These studies demonstrate that both enalapril and nicardipine can effectively reduce blood pressure in patients with hypertension and chronic renal insufficiency. Enalapril but not nicardipine, however, appears to reduce urinary albumin excretion in these patients. Whether the reduction in UAE has any significant impact on the progression of renal disease remains to be established.