In order to evaluate the myocardial injury in cardiac valvular and coronary surgery, variables of creatine kinase[CK], myocardial band of CK[CK-MB], lactate dehydrogenase[LDH], aspartate aminotrasferase[AST] were measured in the preoperative[Preop], the operation day[POD0], and the first[POD1], third[POD3], fifth[POD5], seventh[POD7], ninth[POD9] day after operation in 29 patients. The subjects were divided into two groups according to the diseases: group V [valvular disease, n=16] and group C[coronary artery disease, n=13]. Each group was subdivided into two subgroups according to the duration of aortic crossclamping time[ACT]; group VI[ACT 120min, n=7] and group VII[ACT>120min, n=9]; group CI[ACT 120min, n=6] and group CII[ACT>120min, n=7]. The results were as followed 1. The values of CK between group V and group C had no significant difference. The values of CK in group CII were significantly greater than those in group CI and the values of CK in group VII were significantly greater than those in group VI. 2. Percentages of CK-MB between groups had no significant difference. 3. The serum levels of LDH in group V were significantly greater than those in group C. The serum levels of LDH in group VII were significantly greater than those in group VI. 4. The serum levels of AST in group VII were significantly greater than that in group VI. We were concluded that myocardial injury was more related with the duration of aortic cross clamping time rather than the type of diseases.