A comparison of 265 pairs of standard ECGs and 49-lead precordial maps in 20 patients with ST-segment elevations in anterior ECG leads on admission who eventually were diagnosed as having suffered an anterior Q wave myocardial infarction was carried out to investigate the diagnostic performance provided by the standard ECG in serial studies. Ten patients received intravenous methylprednisolone and 10 were given placebo on admission, and paired map-standard ECG studies were done. ST-segment elevations were taken as an index of ischemic injury and reduction of R wave amplitude or development of Q waves as a marker of developing necrosis. Methods of measurements and derivation of ECG parameters used in the analysis were the same for the standard ECGs and maps. Comparisons of percent change of five ECG-derived variables between 13 time points and admission, as assessed by the six precordial leads of the standard ECGs and the paired 49-lead maps, were made for the entire data base. A separate analysis to assess the performance of the standard ECG was carried out in a comparison of the methylprednisolone and placebo subgroups. In this latter assessment results of comparisons of the standard ECGs from the treatment and placebo cohorts were similar to the conclusions from the comparisons of the corresponding 49-lead maps. Comparisons for the entire 265 pairs of tracings by the two ECG systems demonstrated that the standard ECG is adequate to monitor quantitatively the ischemic injury and necrosis as reflected by the ECG in serial studies throughout the hospitalization and can be effectively employed in lieu of multilead precordial maps in the evaluation of therapeutic modalities for patients with anterior Q wave myocardial infarction.