The antihypertensive effect of the fixed combination of timolol, a beta-blocking agent, hydrochlorothiazide, a thiazide diuretic, and amiloride, a potassium sparing agent, was compared against that of methyldopa in an open study lasting 16 weeks in 32 ambulatory African patients with previously untreated diastolic blood pressure of 95-120 mm Hg. A significant fall in mean diastolic and systolic blood pressure was achieved in both groups up to 8 weeks of treatment and was sustained in the timolol-hydrochlorothiazide-amiloride group during the entire follow-up. In the methyldopa group, mean diastolic and systolic blood pressure rose during follow-up. At 16 weeks the fall in mean diastolic and systolic blood pressure was significantly greater in the timolol-hydrochlorothiazide-amiloride treated patients than in the methyldopa group. Adverse reactions were more frequent and severe in the methyldopa group than in timolol-hydrochlorothiazide-amiloride treated patients. It is concluded that the fixed drug combination of timolol-hydrochlorothiazide-amiloride (Moducren) is effective in controlling mild to moderate hypertension in Africans and is better tolerated than methyldopa in these patients. It is further noted that hypertensive patients can be treated with a combination tablet once a day. This is of crucial significance as it would promote better compliance and, hence, minimize the sequelae of poorly controlled hypertension.