Aim: We study the electrocardiographic abnormalities at time of diagnosis of acute PE in our series of consecutive patients of the last years. We conclude that the electrocardiogram may have diagnostic and prognostic value in patients with acute PE. Methods: We retrospectively reviewed the records of 154 consecutive patients with acute PE.Diagnosis of PE was established by a high-probability ventilation/perfusion lung scan (121 patients), pulmonary angiography or spiral computed tomography (19 patients), or the combination of a suggestive clinical picture with a deep vein thrombosis (DVT) demonstrated by phlebography or echo-doppler (14 patients). Results: Electrocardiogram at time of diagnosis showed abnormalities consistent with acute PE in 107 patients (69.5%). These electrocardiographic abnormalities were: sinus tachycardia in 85 patients (55.2%), S1Q3T3 pattern in 41 patients (26.6%), right bundle branch block in 23 patients (14.9%), T-wave inversion in precordial leads in 22 patients (14.3%), supraventricular tachycardias in 11 patients (7.1%), ST segment depression in 4 patients (2.6%) and P pulmonale in 1 patient (0.6%). Supraventricular tachycardias were: presumed new-onset atrial fibrilation in 8 patients, atrial flutter in 2 patients and paroxysmal supraventricular tachycardia in 1 patient. Conclusion: We might conclude that sinus tachycardia and S1Q3T3 pattern are the principal determinants of severity between the electrocardiographic abnormalities at time of diagnosis in patients with acute PE.