The release sequence of the creatine kinase MM and MB tissue-specific subforms after myocardial reperfusion was elucidated by computer-fitting serial enzyme data from 6 humans in whom coronary flow in the infarct-related artery was angiographically documented as initially zero, opening to normal after angioplasty. The model equation used demonstrated acceptable performance according to standard criteria including visual examination and statistical parameters. The model successfully described the sequential conversion of the MM3 and MB2 tissue isoforms to their respective MM2 and MM1, and MB1 isoforms. Release of MM3 and MB2 was simultaneous, differing in calculated release times by 0.2 to 10%, median 3%. Since MB2 release is not retarded after myocardial reperfusion compared to the more clinically established CK-MM3 isoform, assays for sensitive and rapid measurement of MB2 should be the focus for the non-invasive assessment of myocardial reperfusion due to its higher cardiospecificity.