Creatine kinase is a key enzyme for energy metabolism of contraction and relaxation in skeletal muscle. This enzyme also correlated to mitochondrial oxidative phosphorylation. Distribution of this enzyme is quite wide, including skeletal muscle, myocard, central nervous system, and smooth muscle. Creatine kinase has three main isoenzymes; CK-MM, CK-MB, and CK-BB. Mitochondrial isoenzyme (CKm) is the fourth isoenzyme migrating electrophoretically toward the cathode. Moreover serum creatine kinase isoenzyme (mainly CK-MB and CK-BB) and lesions in the myocard, skeletal muscle, central nervous system, gastrointestinal system, renal and urogenital systems, or acute psychosis, intoxication, pregnancy, labor, and cord blood are also explained. A compendium on CK-BB is also done.