The capacity for recovery of the normothermic left ventricular myocardium from a regional complete ischemia (RCI) was investigated using changes in the myocardial metabolic status (ATP, ADP, AMP, creatine phosphate (CrP), free creatine, glycogen, glucose, lactate) and alterations of the morphology as parameters. In dogs, an area of the anterior wall of the left ventricular myocardium was temporarily deprived completely of its blood supply by 5–7 overlapping ligatures extending into the heart cavity. The metabolites of the adenylic acid-CrP system returned to normal tissue levels after 30 and 60 min of RCI within 14 and 35 days of recovery, respectively; restoration averaged 82% after 100 min, 74% after 140 min, and 38% after 180 min of RCI after 5 weeks of recovery. At the same time glycogen amounted to 163% after 100 min, 114% after 140 min, and 65% after 180 min of RCI. The biochemical data correlated well with the structural changes in the affected myocardium, especially with the amount of de- and regenerating heart muscle cells. These obviously were functionally defect and were not comparable with normal structured and functioning heart muscle cells.