The aim of this randomized double-blind crossover trial was to evaluate the therapeutic efficacy of 100 mg slow-release gallopamil compared to placebo. The results of multistage exercise tests with computer-assisted ECG were analyzed in 16 patients (14 men and two women) aged 39 to 66 years who fulfilled the angiographical evidence of coronary heart disease with stable angina pectoris. All cardioactive medication was withdrawn for the duration of the study except for the trial medication and sublingual nitroglycerin as required. Patients began the therapy with a 5-day placebo run-in period. After this regimen, they were randomized to placebo or slow-release gallopamil (200 mg/day) in two divided doses for 7 days, at the end of which time each patient crossed over to the alternate regimen. Exercise testing was repeated at the end of the run-in period and after 1 week of placebo or active drug therapy. At highest comparable load the ST-segment depression was reduced about 70% before the morning administration (i.e., 12 h after the evening administration) and 6 h after the morning administration. The work load (W x min) increased in 54% or 61% at the maximal possible load. The number of angina pectoris attacks under bicycle ergometer exercise decreased in about 50%. PR-interval was prolonged from 0.14 to 0.15 s. QRS- and OTc-intervals were not influenced. No clinically relevant changes in heart rate and blood pressure were observed. The results indicate great antianginal efficacy and a good toleration of slow-released gallopamil.