32 patients with angina pectoris were treated with lidoflazine for 4.1-12.8 months. During this open study 24 of them showed definite alleviation of angina and a higher exercise tolerance. These 24 patients then entered a placebo- controlled double-blind study for up to 14.5 months, and t hereafter 22 were returned to lidoflazine therapy for up to 9.3 months. Exercise tolerance increased progressively during lidoflazine therapy, receded to pretrial levels during placebo treatment and, after re-institution of lidoflazine, returned to the levels previously attained under lidoflazine. Resting and exercising heart rate decreased on lidoflazine and increased when placebo was administered. These effects paralleled the subjective improvement and deterioration.