Measurement of serum myoglobin, CK-MM isoforms and CK-MB isoenzyme protein are useful for diagnosis and therapy of acute myocardial infarction (AMI). As latex agglutination turbidimetry of serum myoglobin is an easy and rapid assay method, it can be applied for early diagnosis of AMI and its observation of progress after break out of AMI. CK-MM isoforms also can be applicable for early diagnosis of AMI. The assay method of CK-MB isoenzyme protein by immunochemiluminescence is useful for anticipating the infarct size of AMI since this format is not influenced by CK-BB, myokinase, or mitochondria CK.