In a double-blind, placebo-controlled, three-period cross-over, randomized study we evaluated the efficacy and tolerability of a fixed combination of benazepril 20 mg and hydrochlorothiazide 25 mg (BN + HCT) as compared with the fixed combination of captopril 50 mg and hydrochlorothiazide 25 mg (CP + HCT) by ambulatory blood pressure monitoring (ABPM) in patients with mild to moderate hypertension. Eighteen outpatients, 16 men and 2 women aged 41-58 years, were randomized to receive BN + HCT, CP + HCT, or placebo, all administered once daily for 4 weeks according to a three-period cross-over arranged in a 3 x 3 latin square design. Patients were checked after an initial 3-week washout period and every 4 weeks thereafter. At each visit, 24-h ABPM was performed by a noninvasive device (Spacelabs 5300); causal BP and heart rate (HR) were also measured. Both fixed combinations had a clear-cut antihypertensive effect in comparison with placebo.(ABSTRACT TRUNCATED AT 250 WORDS)