The effects of a 12-week oral treatment with tiapamil (200 mg t.i.d.) were compared to those of placebo treatment in a group of 20 men with coronary heart disease. There was a slight reduction of anginal symptoms (p less than 0.05) and a tendency to less nitroglycerin consumption (p less than 0.07). There were no statistically significant differences between the treatments in blood pressure, exercise tolerance during repeated exercise tests, ECG conduction intervals, or routine laboratory tests. No adverse side-effects were encountered. It seems that tiapamil may be beneficial in preventing angina pectoris, but a higher oral dose must be used.