The aim of this study was to compare the effects of ramipril and nitrendipine chronic treatment on urinary albumin excretion (UAE) in hypertensive patients with type II non-insulin-dependent diabetes mellitus (NIDDM) and impaired renal function. A 2-year, prospective, randomised study was conducted on 51 men with a diastolic blood pressure (DBP) > or =95 and < or =105 mm Hg, stable NIDDM, serum creatinine between 1.6 and 3.0 mg/dl and persistent UAE >300 and <2000 mg/24 h. After a 3-month preliminary observation period, during which patients began a low-protein, low-sodium diet, and a subsequent 4-week run-in period on placebo, patients were randomly treated with ramipril 5 mg or nitrendipine 20 mg for 2 years. Both drugs similarly reduced BP without affecting glucose homeostasis. In the ramipril group UAE significantly decreased after only 3 months of treatment, whereas in the nitrendipine group a significant although lesser reduction in UAE was observed only after 1 year. During the second year the UAE% change was not statistically different between the two treatments. Serum creatinine and creatinine clearance showed no significant change with both drugs. The progression of renal insufficiency as assessed by the rate of reduction of creatinine clearance over the 2 years of the study was similar in the ramipril and the nitrendipine groups. In conclusion both ramipril and nitrendipine were associated with a decrease in UAE although such a reduction was earlier and more marked with ramipril. The decline of renal function did not differ significantly between the two treatments.