The antihypertensive efficacy and acceptability of perindopril (P) were compared to those of captopril (C), atenolol (A) and a diuretic, hydrochlorothiazide + amiloride (D), in 3 double-blind parallel multicenter studies involving 165, 173, and 165 patients, respectively. Patients with essential hypertension and a supine DBP between 95 and 125 mmHg (mean 103.9, 106.2, and 105.2 mmHg, respectively) after a 1-month placebo period were randomized to P 4 mg once daily (o.d.) and either C 25 mg twice daily, or A 50 mg o.d. or D (hydrochlorothiazide 50 mg + amiloride 5 mg o.d.) and treated for 3 months, with visits at monthly intervals. If necessary, treatment was adjusted at each visit to control BP (supine DBP less than or equal to 90 mm Hg): firstly by doubling the dose and secondly, one month later, by the addition of a second drug, a diuretic in the studies versus C or A, a beta-blocker in the study versus D. At 3 months, BP control on monotherapy in the three studies was achieved in the following proportion of patients: 49% with P vs 49% with C; 55% with P vs 48% with A; 72% with P vs 72% with D. Most of the patients controlled by P received 4 mg, about 15% were controlled with 8 mg. A further percentage of patients was controlled with combination therapy, the combination with a diuretic being more effective with P than with C (26 vs 8%) or A (23 vs 10%) and the combination with a beta-blocker being less effective with P than with D (5 vs 13%). The total percentage of patients controlled was greater with P than with C (75 vs 57%, p = 0.016) or A (78 vs 58%, p = 0.006) and there was no significant difference between P and D (78 vs 84%). The drop-out rate due to side-effects was up to 6% with P, similar to that observed with C (4%), A (5%) and D (5%). Most of the complaints reported with P were minor and non-specific, their incidence being similar to that observed with the other drugs. Cough was reported with both P (1%) and C (2%) as well as with A (1%) and D (1%). Compared to these drugs, the biological acceptability of P was good, no case of renal failure being observed.(ABSTRACT TRUNCATED AT 400 WORDS)