This study evaluated the safety, antianginal and antiischemic effects of amlodipine, a dihydropyridine calcium antagonist, in patients with chronic stable angina pectoris. The patients (n = 29) were evaluated during a 26-week single-blind dose titration phase followed by a 6-week double-blind placebo-randomized withdrawal phase. No patient withdrawals resulted from adverse events directly related to amlodipine. A comparison of the antianginal effects of amlodipine in the single-blind phase with the placebo phase showed a reduction in anginal episodes (p less than 0.001) and a decrease in sublingual nitroglycerin usage (p less than 0.01) that persisted in the treated double-blind group (n = 12). The place-bo double-blind group (n = 10) had a reduction in anginal episodes, but no significant change in sublingual nitroglycerin usage. The antiischemic effects of amlodipine were evident; there was an increase in exercise tolerance and a reduction of ST-segment depression, as seen in the 24-hour after-dose (range 23 to 30 hours) exercise tread-mill test. During single-blind therapy, total exercise time (p less than 0.001) and time to 1 mm ST depression (p less than 0.001) displayed an overall improvement. During the double-blind phase, the treated group demonstrated an improvement in total exercise time (p = 0.01) while the placebo group had no significant change. The total amount of ST depression also differed between treated and placebo groups (1.2 +/- 0.12 vs 1.8 +/- 0.17 mm, respectively, p less than 0.01). These results lend support to the clinical safety of this medication used as once-a-day therapy.