The purpose of this study was to investigate the efficacy and safety of labetalol, an alpha and beta-adrenergic receptor blocking agent in 32 patients aged from 72 to 97 years (mean = 85 years) with blood pressure (B.P.) greater than or equal to 160/95 mmHg. This study was carried out in a double-blind, randomized, placebo-controlled design. After 6 weeks of treatment with labetalol (mean dose = 235 +/- 47.5 mg/day), the systolic pressure was lowered from 187 +/- 24 to 145 +/- 28 mmHg (p less than 0.001) and the diastolic pressure from 98 +/- 10 to 82 +/- 9 mmHg (p less than 0.001). Likewise, in the placebo group, both systolic and diastolic pressures were significantly reduced but the changes were significantly greater in the labetalol group, -33 +/- 26 versus -13 +/- 20 mmHg and -14 +/- 10 versus -8 +/- 14 mmHg respectively. Labetalol achieved B.P. control (160/95 mmHg) in 64% of the treated patients, compared to 40% in the placebo group. Two patients on labetalol discontinued their treatment due to side-effects (one bradycardia and one cutaneous reaction) compared with one patient on placebo (cardiac failure). Two other cases in the labetalol group had side-effects (one fatigue and one dizziness) which prevented increasing the treatment as necessary.