A randomized, placebo-controlled, double-blinded trial was performed to evaluate the usefulness of empiric therapy with a calcium antagonist in patients who undergo coronary angioplasty. A total of 201 patients were randomized to placebo or to high-dose diltiazem (mean dose, 329 mg/day). Treatment began 24 hours before angioplasty. Restenosis was assessed by percent area stenosis as determined by quantitative angiographic techniques before, immediately and 1 year after angioplasty. All patients also received aspirin and dipyridamole before angioplasty. Heparin and verapamil were administered intravenously during the procedure. The 2 groups were similar with respect to age, extent of coronary artery disease, smoking history, and baseline lipid levels. Procedural complications, including death (1 vs 1), Q-wave infarction (0 vs 3), acute occlusion (5 vs 5) and focal spasm (0 vs 0), were not significantly different in the diltiazem and placebo patients, respectively. Freedom from all acute complications was noted in 85% of patients in both groups. One-year angiographic follow-up was obtained in 60% of patients. Restenosis rates were similar: 36% in the diltiazem group and 32% in the placebo group (p = 0.30). The incidence of late cardiac events (death, Q-wave myocardial infarction, recurrent angina or coronary bypass graft surgery) was similar in the 2 groups. Thus, diltiazem did not influence the overall restenosis rate or prevent late events after coronary angioplasty.