Practolol and sotalol were found to differ qualitatively in their effects on blood pressure (BP). The reductions in both systolic and diastolic BP and in heart rate were largely unrelated to differences in dosage and serum concentrations of practolol in 22 patients with mild‐to‐moderate hypertension. On the other hand, when due to sotalol, these effects were dose related in 12 patients. From 200 to 800 mg of both drugs were given daily in two doses. The differences from the posttreatment of placebo systolic/diastolic BP were at a maximum at 400 mg of practolol: 22/6, 18/9, and 18/6 mm Hg in a standing, sitting, and supine position. In 8 patients who tolerated 600 mg of sotalol, the differences were, respectively, 29/14, 22/18, and 27/18 mm Hg. Side effects with sotalol were numerous when the heart rate fell below the critical level of about 48. The highest tolerated serum concentration of sotalol was about 5.1 mg/1. A 600 mg dose of sotalol was tolerated as well and as often as 800 mg of practolol. The serum concentrations of both drugs were closely related to the dose per kilogram of body weight.