Total CPK activities and CPK isoenzymes fractions of the sera and some organ tissues of dogs were examined to acquire the basic data of canine CPK available in clinical practice. In addition fluctuation of serum total CPK activities and CPK isoenzymes fractions is artificially induced canine myocardial infarctino were investigated to know the availabity of them as indicators for the diagnosis of myocardial infarction. For the determination of serum total CPK activities, total 22 clinically healthy dogs(7 to 30 months old, 15 of female and 7 of male) were used and 15 out of 22 dogs were used for the determination of serum CPK isoenzymes fractions. For the determination of total CPK activities and CPK isoenzymes fractions. some organ tissues (the hearts, skeletal muscles and brains )from 3 dogs were examined. For the fluctuation of total CPK activities and CPK isoenzymes fractions in the sera from artificially induced canine acute myocardial infarction, 3 dogs of coronary artery ligated experimental group and 3 of control group were used. The results obtained were as follows ; 1. Serum total CPK activities of normal dogs were 106.2${pm}$29.9(31.3∼148.1)IU/$ell$. 2. The pattern of serum CPK isoenzymes fractions in normal dogs was high with decreasing order of CK$_1$>CK$_3$>CK$_2$. 3. Total CPK activities of organ tissues were high with decreasing order of the skeletal muscles > the hearts > the brains. 4. The pattern of CPK isoenzymes fractions of the organ tissues was high with decreasing order of CK$_3$>CK$_2$ in the hearts and only CK$_3$(100%) was detected in the skeletal muscles. Further they were high with decreasing order of CK$_1$>CK$_3$>CK$_2$ in the trains. 5. Serum total CPK activities in experimental group were changed with higher values than those of control group. 6. In the fluctuation of serum CPK isoenzymes fractions the CK$_1$ CK$_2$ and CK$_3$ values were changed with higher values than those of control group. 7. It was become clear that the finding of Increase of serum total CPK activities, and CK$_2$ and CK$_3$ was important for the diagnosis of myocardial infarction.