The effects of diltiazem, 240 mg/day, were studied in 12 patients with chronic exertional angina and angiographically proven coronary artery disease, who received maintenance therapy with propranolol. Mean age was 60.1 years (range 46 to 67). Patients received propranolol, 60 to 240 mg/day, before and during the study. A double blind, placebo controlled, cross-over design was used to test the effect of added diltiazem, during 8 weeks. Duration of exercise varied from 398 +/- 30 (mean +/- SEM) to 419 +/- 37 (placebo) or 469 +/- 35 sec (diltiazem) (NS). Time to appearance of angina varied from 283 +/- 32 to 313 +/- 34 and 302 +/- 27 sec, respectively (NS). Resting and maximal effort heart rate and blood pressure did not differ among basal, placebo and diltiazem conditions. Segmental wall motion analysis by radioisotopic ventriculogram revealed dyskinetic zones during placebo or diltiazem therapy. Basal ejection fraction did not increase during exercise and this was not modified by diltiazem or placebo. Thus, the addition of diltiazem to propranolol in patients with chronic, exertional angina failed to modify angina threshold, exercise duration or left ventricular performance.