A number of ECG abnormalities can be observed in the acute phase of pulmonary embolism (PE). Their prognostic value has not yet been systematically studied in large patient populations. In 508 patients with acute major PE derived from a large prospective registry, the current authors assessed, on admission, the impact of specific pathological ECG findings on early (30-day) mortality. Atrial arrhythmias, complete right bundle branch block, peripheral low voltage, pseudoinfarction pattern (Q waves) in leads III and aVF, and ST segment changes (elevation or depression) over the left precordial leads, were all significantly more frequent in patients with a fatal outcome. Overall, 29% of the patients who exhibited at least one of these abnormalities on admission did not survive to hospital discharge, as opposed to only 11% of the patients without a pathological 12-lead ECG. Multivariate analysis revealed that the presence of at least one of the above ECG findings was, besides haemodynamic instability, syncope and pre-existing chronic pulmonary disease, a significant independent predictor of outcome. In conclusion, ECG may be a useful, simple, non-costly tool for initial risk stratification of patients with acute major pulmonary embolism.