France1 Two hundred and eleven patients with mild or moderate hypertension, mean age 53.5 + 9.5 years (range 24-70) were randomised double-blind to treatment with either captopril 50 mg (C50), hydrochlorothiazide 25 mg (HCTZ25), the fixed combination of captopril 50 mg and hydrochlorothiazide 25 mg (C50/HCTZ25) or placebo. 2 Blood pressure, heart rate, body weight and side effects were assessed at the end of the run-in period on placebo and after 4, 6, 8 weeks treatment at the same time, 20-24 h after the last dosing. Routine biochemical examinations were carried out on all patients after the placebo period as well as after 4 and 8 weeks. 3 Blood pressure significantly decreased in all groups, but the mean percentage change from baseline was highly statistically significant at 8 weeks, for C50 and C50/HCTZ25 groups. 4 The incidence of clinical side effects was low and not statistically different for the four groups with few specific adverse effects (one transient alteration of taste in captopril group). No patient was withdrawn from the study due to side effects. 5 A better anti-hypertensive efficacy was obtained with the fixed combination captopril 50 mg/hydrochlorothiazide 25 mg once daily compared to placebo or each component alone, and without any difference in side effects.