Age, race, pretreatment blood pressure and plasma renin activity have been related to the antihypertensive response to calcium antagonists in studies that included 215 patients with mild to moderate essential hypertension. Adverse effects necessitated withdrawal from therapy in about 10% of the patients. All calcium antagonists lowered blood pressure significantly and comparably without weight gain or reflex tachycardia. In a multiple linear regression analysis of 138 white patients, age, pretreatment blood pressure and renin activity were of independent and significant predictive value for the antihypertensive response. Stratification of patients into 3 age groups disclosed a greater effect in patients older than 60 years compared with those between 40 and 60 years and those below 40 years, respectively (p less than 0.01). In 16 middle-aged black patients, antihypertensive therapy with a calcium antagonist proved highly efficacious. Monotherapy with a calcium antagonist may become a first-line treatment for essential hypertension, particularly in older patients who have low renin activity and possibly in black patients as well.