PURPOSE: To evaluate the effectiveness and tolerance of the association of captopril 50mg and hydrochlorithiazide 25mg in hypertensive patients with diastolic pressure between 95 and 115 mmHg. METHODS: An open, multicenter and non-comparative study was performed. After 2 weeks of placebo, the patients received ½ tablet of drug association. Patients were evaluated after 4, 8 and 12 weeks, and those who had diastolic pressure >90mmHg after 8 weeks of therapy received 1 tablet/day. RESULTS: The results of 433 patients were analyzed: 47±10 years old, 30% female, 76% white. Initial systolic and diastolic pressures were 156±16 and 103±11mmHg and after 14 days of placebo were 156±15 and 103±9mmHg (p>0.05). Systolic/diastolic pressure after 4, 8 and 12 weeks of treatment reduced progressively (p<0.05) to 143±14/95±11, 140±13/91±9 and 134±11/86±8mmHg. Blood pressure control was observed in 45, 67 and 88% (p<0.05) of patients after 4, 8 and 12 weeks. Cough was the most important symptom, registered in 7% of patients under placebo and 12% in patients under treatment. The tolerance was considered good for 98% of patients. CONCLUSION: The association of captopril with hydrochlorothiazide is effective with good tolerance, being indicated as a once a day monotherapy for mild and moderate hypertension.