As described in the preceding communication, either propranolol hydrochloride or hydrochlorothiazide were randomly allocated in a double-blind manner to 683 patients with initial diastolic BP in the range of 95 to 114 mm Hg. Of this number, 394 entered the long-term treatment phase. During the subsequent 12 months of long-term treatment, hydrochlorothiazide was more effective than propranolol in controlling BP (mean reductions, -17.5/-13.1 mm Hg with hydrochlorothiazide compared with -8.3/-11.3 with propranolol. After treatment with hydrochlorothiazide, a greater percentage of patients achieved the goal diastolic BP of less than 90 mm Hg (65.5% compared with 52.8% taking propranolol). Also during treatment, fewer patients receiving hydrochlorothiazide required termination as compared with those receiving propranolol; comparative dosage requirements were lower; additional titration during long-term treatment was required less often, and BP remained lower after withdrawal of the active drugs. However, biochemical abnormalities were greater with hydrochlorothiazide. Although not statistically significant, the antihypertensive effects of hydrochlorothiazide were greater in blacks than in whites. Whites, on the other hand, had a greater response to propranolol than blacks, although it was still less than the response of the whites to hydrochlorothiazide.