1. In a multicentre double-blind study, oxprenolol (OX) hypotensive effect was investigated in 329 patients with mild to moderate hypertension.
2. A factorial experimental design with three factors was chosen: OX mg/day 0, 20, 40, 60, 80; dihydrazinophthalazine (DHZ) mg/day 0, 30; and hydrochlorothiazide (HCH) mg/day 0, 30. Each treatment was carried out for a period of 4 weeks after an adequate placebo period.
3. Independently of the association with DHZ and/or HCH, OX yielded a hypotensive effect linearly related to dose (P < 0.05) for systolic and diastolic pressure in the standing position, but only for diastolic pressure in the supine position.
4. The addition of DHZ and/or HCH to OX at 80 mg/day caused a significant increase in the final hypotensive effect.