Few studies have been devoted to the role of calcium blockers in stable angina of effort. For this reason, we undertook, a double-blind, randomized study with placebo, to compare the effects of diltiazem (D) and nifedipine (N) on the ergometric parameters of 20 patients with angina of effort and with mono- or multivessel disease. The study protocol extended over 3 weeks and included a reference stress test, 8 days of placebo followed by a repeat yesy, an then 15 days during which each patient received 180 mg of D and/or 30 mg of N in cross-over. A stress test was performed at the end of each week. The calcium blockers appeared to improve the effort tolerance, the duration of the ergometric test and the amplitude of the maximal ST segment depression. Diltiazem showed itself to be superior to nifedipine by the absence of side effects and by an improved cardiac performance on effort.