In six anesthetized dogs with myocardium partially damaged by ischemia (LAD occlusion), the effect of an i.v. bolus injection of 0.05 mg molsidomine/kg body weight followed by a 6-h i.v. infusion of 0.5 micrograms molsidomine/kg/min on the volume of myocardial ischemia, the relative remaining blood flow in the ischemic area, and the dynamics of the left ventricle were examined by means of computer tomography. The extent of the ischemic volume in the group treated with molsidomine was by far lower than in the control group; this difference was significant if one takes into account the individual heart size. The relative remaining blood flow in the ischemic region was not influenced by molsidomine. The reduction of preload and afterload resulted in corresponding changes in left ventricular areas, segments of these areas, the long axis, thickness of myocardium, ejection fraction and stroke volume. Aortic pressure was lowered insignificantly, heart rate remained nearly unchanged. Plasma analyses of molsidomine. SIN 1 and SIN 1C show that the applied dosage was sufficient to reach a constant concentration over the whole period of observation in the dog.