The aim of the study was to evaluate the clinical and renal hemodynamic effects of cilazapril in 10 hypertensive patients with moderate-to-severe chronic renal failure (creatinine clearance 14-50 ml/min). After 2 weeks of placebo, cilazapril 0.5 mg/day was given, and the dose was increased up to 5 mg/day if sitting diastolic blood pressure (SDBP) was not normalized (less than or equal to 90 mm Hg). Once a normal SDBP value was achieved, the patients remained on the given dose regimen for 6 months. After this period SDBP decreased from 107 +/- 2 to 95 +/- 2 mm Hg (p less than 0.001). At the end of treatment, glomerular filtration rate (GFR) remained unchanged in five patients, improved in four patients, and slightly decreased in one patient, the slope from baseline being 0.137 and the variation of GFR per unit of GFR at baseline being between -0.20 and 0.47. Likewise, effective renal plasma flow increased not significantly, showing considerable variability. Urinary protein excretion was reduced significantly from 2.51 +/- 0.75 to 0.51 +/- 0.10 g/L (p less than 0.05), suggesting that converting enzyme inhibition may exert a renal protective effect. In conclusion, it appears that cilazapril does not induce functional damage in the kidney of predialysis hypertensives.