This study was attempted to evaluate the effectiveness of cold cardioplegic solution [group B] compared with that of intermittent aortic cross clamping [group A]. 1. In group A, two dogs recovered spontaneous heart beat without using defibrillator and one case was used defibrillator once. In group B, four dogs recovered the spontaneous heart beat even without defibrillator and in one animal the defibrillator was used three times. 2. There was no significant difference in serum electrolyte [Na+, Ca2+, Cl- ] between group, but K+ level was decreased in both group. 3. The group A showed more increasing in serum LDH activity than group B. 4. The postoperative myocardial ATP level was $2.35{pm}0.10$ ${mu}$M/Gm. of wet weight in control group, $1.46{pm}0.16$${mu}$M/Gm. of wet weight in group A [60.2% of control group], and $1.80{pm}0.14$${mu}$M/Gm. of wet weight in group B [76.8% of control group].