The introduction of calcium entry blockers which caused marked vascular smooth muscle relaxation with minimal effects on myocardial contractility have provided a new approach to the patient with angina due to coronary artery spasm. Multiple, double-blinded, randomized studies of diltiazem versus placebo have demonstrated that this agent results in reduction in angina frequency and nitroglycerin consumption by 30% to 70% with a demonstrated dose response. A long-term, open label follow-up study of 18 patients who participated in a 44-week prospective, double-blind crossover trial of 240 mg of diltiazem versus placebo for prophylaxis of angina in patients with coronary artery spasm demonstrated a 75% decrease in angina attacks during the first five months of the study and an 80% decrease compared to the placebo period during the second six months. Both the short- and long-term studies have demonstrated very few adverse side effects, less than 7%. A recent long-term study of 43 patients who took diltiazem regularly and were followed in the Coronary Artery Spasm Clinic at Stanford University Medical Center for a mean of 19.6 months (range 6 to 28.5 months) was analyzed for cardiovascular events in the 19.6 months prior to therapy and the 19.6 months after the initiation of therapy. Cardiovascular events on diltiazem, including sudden cardiac death, myocardial infarction, and hospitalization to rule out myocardial infarction utilizing a binomial distribution showed over a 90% reduction compared to the pre-diltiazem period. Adverse effects were reported in six patients who reported minimal to mild pedal oedema.(ABSTRACT TRUNCATED AT 250 WORDS)