Thirty-four patients with coronary heart disease who had silent myocardiac ischemic episodes as evidenced by long-term ECG monitoring were examined. Silent ST-segment elevations and depressions were encountered 2.7- and 4.9-fold as compared to manifest ones. The fact that the CHD patients had silent ST-segment depressions and/or prolonged high-amplitude silent ST-segment elevations suggests a grave severity of abnormal myocardial processes. There was a reduction in the number, duration of silent ST-segment elevations and depression episodes and in the amplitude of silent ST-segment depressions. This may indirectly indicate that the agent affects predominantly coronary blood flow and coronary vascular tone.