The aim of this work was to study the effect of early administration of angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II type-I receptors blockers (ARB) on renal function and proteinuria in renal transplant recipients with good, stable renal function and mild proteinuria. Twenty four patients started ACEI/ARB therapy within 14 months after surgery (RAS-). Before (T0) and every month for 2 years after the initiation of ACEI/ARB we evaluated creatinine clearance (CrCl), proteinuria/day (UP), UP/CrCl (FUP), arterial blood pressure, and serum lipid levels. Twenty-eight patients who never received ACEI/ARB (RAS+) were studied in the same fashion. In the RAS+ CrCl was reduced after 2 years compared with T0 (64.5 +/- 2.6 vs 75.0 +/- 3.2 mL/min, P < .003); UP and FUP were both significantly increased (666 +/- 65 vs 132 +/- 20 mg/day 8.8 +/- 1.2 vs 2.6 +/- 0.6 mg/mL x 10(3); P < .001 and .002) compared with T0. Moreover, UP (P < .04), FUP (P < .03), and the percentage reduction of CrCl (11.4% +/- 5% vs 4.6% +/- 1.8%; P < .05) were greater in RAS+ than RAS- subjects at 2 years of the study. The values of other parameters did not show significant differences between the two groups. In conclusion, this study suggested that ACEI/ARB have renoprotective effects, when used in patients with good stable renal function and mild proteinuria. These drugs may play a role to prevent chronic allograft nephropathy.