The efficacy and tolerability of Prinivil and Procardia XL were compared in 135 (67 black, 68 white) patients with mild to moderate uncomplicated essential hypertension. The goal of therapy was to achieve and maintain a supine diastolic blood pressure (SDBP) of > 90 mmHg or a decrease in SDBP > or = 10 mmHg. Patients received Prinivil 10 to 40 mg once daily or Procardia XL 30 to 120 mg once daily during a titration period of 2 to 8 weeks to achieve the goal blood pressure before a 4-week maintenance period. The mean baseline supine systolic/diastolic blood pressures were 151/97 mmHg in patients receiving Prinivil and 153/99 mmHg in patients receiving Procardia XL. Ninety-one percent of patients receiving Prinivil and 95% of those receiving Procardia XL achieved SDBP control at the end of titration therapy. At the end of the maintenance treatment period, 79% of patients receiving Prinivil and 80% of those receiving Procardia XL had SDBP control. Mean decreases in SDBP from baseline were comparable for both treatment groups. At the end of the titration period, mean decreases were 9.6 mmHg in patients receiving Prinivil and 11.3 mmHg in patients receiving Procardia XL; at the end of the maintenance period, mean decreases were 10.8 mmHg and 12.1 mmHg, respectively. There were no differences in treatment responses in either the black or white hypertensive subgroups. Thus both drugs were equally effective in black and white patients with mild to moderate essential hypertension. Both drugs were generally well tolerated, but the number of adverse experiences requiring discontinuation of therapy was significantly higher (P = 0.03) in patients receiving Procardia XL.