To maximize the information one can obtain from the temporal curves of creatine kinase (CK) after acute myocardial infarct (AMI), the authors tested how well the curves were fit by three functions: the log-normal function, the gamma function, and the function of Schwerdt and associates (Cardiovasc Res 1990;24:328-334). The log-normal function fit best. Using time course curves of the isoenzyme CK-MB in 16 patients with AMI, the authors found that the integrated area under the fitted log-normal function correlated closely with the postinfarct ejection fraction. Together, the success of the log-normal function and mathematical analysis of the kinetics of CK-time curves impose a form on the release of CK from the heart, and they imply that k, the first-order rate constant of loss of CK from the serum, may be indeterminate from the CK-time curve alone. Although this indeterminancy of k helps explain the prior successes and failures in sizing AMIs from CK-time curves, it should not discourage one from obtaining important quantitative and prognostic information from these CK-time curves. It does suggest that such associations will be largely empiric.