The antihypertensive efficacy and tolerability of two betablockers: atenolol and bopindolol, was compared in a group of 30 elderly subjects aged 64.8 +/- 4.6 years. The daily dose of the two agents was relatively low. Atenolol 50-100 mg and bopindolol 0.5-1.0 mg sufficed to cause reduction of DBP to the target of less than or equal to 95 mm Hg, when applied as monotherapy. This was achieved in 75% of cases with bopindolol and in 93% of cases with atenolol. Atenolol, 50-100 mg/dd, lowered blood pressure from 173.7 +/- 13.2/103.7 +/- 3.0 (weekly) to 155.5 +/- 16.5/86.5 +/- 8.2 mm Hg (week 12) (P less than 0.005) while bopindolol, 0.5-1.0 mg, lowered blood pressure from 171.6 +/- 11.3/104.1 +/- 3.6 to 158.7 +/- 20.9/86.1 +/- 6.0 mm Hg (P less than 0.005). Heart rate was reduced from 80.5 (week 4) to 66.7 +/- 7.3 (week 12) by atenolol (P less than 0.0001), and from 83.7 +/- 11.8 (week 4) to 71.1 +/- 7.5 (week 12) by bopindolol (P less than 0.0001). Between treatment differences: comparisons yielded P values which were not sufficiently low to reject the null hypothesis of no difference between the two treatments. Well-being and short-term memory were not affected by either agent and tolerability of both drugs was good. These findings demonstrate that both bopindolol and atenolol are useful agents for control of hypertension in the elderly.