Calcium antagonists work by blocking the entrance of calcium from the outside of the cell to the inside of the cell through the voltage-dependent calcium channels. There are three major L-type (high voltage) calcium channel blocker sites (a dihydropyridine site for nifedipine, a phenylalkylamine for verapamil, and a benzothiazepine site for diltiazem) and a tetralol T-type (low voltage) calcium antagonist. Calcium antagonists differ in terms of their tissue affinity and vascular selectivity resulting in different therapeutic applications. The initial disadvantage of a short-half has been overcome with drug delivery systems that lower blood pressure over a twenty-four hour period. These calcium antagonists are effective in lowering blood pressure and reducing anginal episodes in African Americans and whites, regardless of age or renin level.