The objective of this study was to compare the efficacy and the safety of bisoprolol (B) and acebutolol (A) on blood pressure at rest and during exercise in hypertensives. The design was a comparative, single-blind study with two phases following a 10-day washout period for pretreated patients: a 15 day-placebo phase and an 8-week therapeutic phase. Forty-six outpatients suffering from mild to moderate essential hypertension [diastolic blood pressure (DBP) ranging between 95 and 120 mm Hg] were randomly given either 10 mg of bisoprolol or 400 mg of acebutolol once a day for 8 weeks; this dosage was doubled after 4 weeks if DBP was still above 90 mm Hg. Blood pressure measurements were made 24 h after drug intake at rest and during exercise stress tests and were performed at the end of the placebo period and after 1 and 2 months of active treatment. Serum lipid levels were also measured before and at the end of the study. Forty-four patients (21 B/23 A) were analyzed for resting blood pressures and 33 (15 B/18 A) for exercise blood pressure profile. At the end of the first month of treatment, a significant decrease (p < 0.001) in supine and upright systolic (SBP) and DBP was noted in both groups. The reduction in supine DBP after 4 weeks was significantly greater with B (p = 0.036). A further decrease of blood pressure was observed in both groups during the second month of treatment, which was significant only in supine SBP (p < 0.05). After 2 months, the heart rate decreased by 24% with B and 13% with A (B vs. A; p = 0.002). Regarding the BP profile during exercise, B and A caused a similar and significant reduction in both SBP and DBP (p < 0.001). The reduction in heart rate during exercise was more marked with B, with no significant difference between the two groups. Side effects were reported in three patients on B and six on A. Both at rest and during exercise, at a level of effort similar to that of daily activities, B exerted a hypotensive effect at least equivalent to that of A in mild and moderate hypertensive patients.