Using serial M-mode echocardiographic determinations of left ventricular (LV) mass and function, the effects of dilevalol, a selective β2 agonist with nonselective β-antagonist properties, were compared with those of metoprolol in 2 centers in doubleblind, randomized clinical trials using similar protocols in nonelderly hypertensive patients (aged < 65 years) (study 1). In a separate bicenter study with a similar design, dilevalol was compared with atenolol in elderly hypertensive patients (aged ≥65 years) (study 2). Patients in both studies received placebo for 2 to 4 weeks, and were then randomized to receive increasing doses of dilevalol (200, 400, 800, 1,600 mg) or metoprolol (100, 200, 300, 400 mg) in study 1, and dilevalol (100, 200, 400, 800 mg) or atenolol (50, 100 mg) in study 2, to achieve a supine diastolic blood pressure (BP) of < 90 mm Hg. In both studies, LV function and mass (Penn convention) were determined by echocardiographic examinations performed before randomization and at the end of the active treatment phase. Dilevalol, metoprolol and atenolol significantly reduced BP compared with placebo. In the nonelderly patients, a modest reduction in LV mass was observed with dilevalol (p < 0.03) but not with metoprolol. Indexes of LV function-as assessed by end-diastolic and end-systolic dimensions, LV ejection time and ejection fraction-were better preserved by dilevalol than by metoprolol. In the elderly, neither dilevalol nor atenolol affected LV mass; however, indexes of LV function were better preserved with dilevalol than with atenolol. In conclusion, in these studies dilevalol was shown to be an effective antihypertensive drug with BP-lowering effects comparable to those of atenolol and metoprolol in nonelderly and elderly patients. LV function was preserved better by dilevalol than by atenolol or metoprolol, and LV mass was reduced moderately by dilevalol in nonelderly patients only. © 1989.