To assess the efficacy and safety of 2.5, 5, and 10 mg bisoprolol/6. 25 mg hydrochlorothiazide (HCTZ), 2.5, 5, and 10 mg amlodipine; and 5, 10, 20, and 40 mg enalapril in subjects (n = 541) with a sitting diastolic blood pressure of 95 to 114 mm Hg, data from two comparative studies were pooled. All drugs were titrated to a diastolic blood pressure 90 mm Hg or less. Both studies were double-blind, randomized, parallel dose escalation trials with similar designs and included three active treatments. The second study also had a placebo group. The mean change from baseline of systolic and diastolic blood pressure for placebo (n = 79) was -0. 1/-2.2 mm Hg; amlodipine (n = 154), -12.4/-10.3 mm Hg; enalapril (n = 155), -9.4/-8.2 mm Hg; and bisoprolol/HCTZ (n = 155), -14.0/-12.0. Overall efficacy analyses documented a statistically significant decrease in sitting diastolic blood pressure for bisoprolol/6.25 mg HCTZ compared with placebo, amlodipine, and enalapril. There was a significant reduction in sitting systolic blood pressure for bisoprolol/6.25 mg HCTZ compared with placebo and enalapril but not amlodipine. Also, there was a significant decrease in sitting heart rate for bisoprolol/6.25 mg HCTZ (-6.2 beats/min) compared with placebo (+0.1 beats/min), amlodipine (+1.2 beats/min), and enalapril (+0.5 beats/min). The control rate (diastolic blood pressure < or = 90 mm Hg) for bisoprolol/6.25 mg HCTZ (66.5%) was significantly better than for placebo (21.8%) and enalapril (47.1%) but not amlodipine (58.4%). Of those patients achieving and maintaining control, 49% of the bisoprolol/6.25 mg HCTZ subjects were on the lowest two doses compared with 30% of the amlodipine and 26% of the enalapril subjects. Percentages of patients reporting at least one drug-related adverse event through week 12 were 27%, 24%, 28%, and 25% for placebo, bisoprolol/6.25 mg HCTZ, amlodipine, and enalapril (not significant). Lower doses of two drugs in fixed combination can provide as good or better blood pressure control compared with higher doses of a single drug with similar tolerability and safety.