The effects of placebo and of a spironolactone-althiazide combination in the treatment of twenty-two Kenyan Africans with hypertension were assessed using a double-blind technique. After a 2-week medication-free period, patients were randomly allocated to placebo or active treatment for 6 weeks then crossing over to the alternative medication for a further 6 weeks, reverting to the original medication for a final 6 weeks. 100 mg spironolactone plus 60 mg althiazide per day was found to produce greater falls in blood pressure when compared with the placebo periods, sometimes significantly. No serious side-effects were reported. Electrolytes remained within normal limits.