The relationship between asynergy of the left ventricular wall detected by two-dimensional echocardiography and ECG signs of necrosis (number of Q waves greater than or equal to 40 ms, Wagner's score) was evaluated in 315 patients (NYHA I-II) 23-90 days after a first Q-wave myocardial infarction (MI). Poor correlations were found between asynergy and ECG parameters. An ECG anterior MI is an apicoseptal MI by echo (independently of the ECG extent of Q waves) and the ECG is of little or no help in predicting the extent of asynergy to the inferior wall and proximal segments of the septum. An ECG inferior MI is inferoposterior by echo and the ECG has very limited value in predicting the extent of asynergy to the apex and septum. Patients with Q waves in leads II, III, and aVF had more extensive asynergy than those with either 2Q or greater than 3Q. R/S greater than or equal to 1 in V1 and/or V2 was present in 44% of patients with inferior MI while asynergy of at least one segment of the posterior wall was observed in 94%. In conclusion, standard ECG is sensitive in identifying anterior versus inferior infarct but it is unreliable in predicting the real extent of asynergy of the left ventricle, particularly in inferior infarcts.