Abstract The pharmacokinetic properties of quinapril were evaluated in 6 hypertensive patients with normal renal function (group A), 4 hypertensive patients with mild-to-moderate renal dysfunction (group B), and 3 hypertensive patients with severe renal dysfunction (group C). Assessments were made after patients received a single oral 10-mg dose of quinapril and after they received 8 consecutive days of treatment. The peak drug level and the area under the curve for quinaprilat (the active metabolite of quinapril) were 2 to 4 times higher in group C than in group A after 8 days of treatment; this difference was statistically significant. A significant correlation between the area under the curve and serum creatinine levels was observed after the single dose and after 8 days of treatment. Based on our results, we recommend that patients with renal dysfunction receive only half the dose of quinapril administered to patients with normal renal function.