We describe our experience with 1000 electric cardioversions performed at the emergency ward in the Hospital of Cardiology y Neumology, National Medical Center I.M.S.S. The objectives are: 1. Report our experience. 2. Investigate if digitalis treatment should be discontinued before the procedure. 3. Determine if all patients should be on anticoagulant therapy for elective cardioversion. 4. Indicate the optimal anesthetic drug with minimal side effects. A therapeutic procedure was performed in 73% of our cases and an elective one in the remaining 27%. Patients were grouped as ischemic heart disease 26%, rheumatic heart disease 24%, chronic obstructive pulmonary disease 14%, systemic hypertensive heart disease 13%, without clinical heart disease 6%, preexcitation syndrome 6%, adult congenital heart disease 4%, with implanted pacemaker 2%, pregnancy 2% and diverse myocardial diseases 2%. As a cardiac arrhythmias atrial fibrillation was the main cause 45%. Atrial flutter represented 25%, atrial paroxysmal tachycardia was 21% and ventricular tachycardia 9%. A cardioversion was performed in 43% of patients under digitalis treatment at therapeutic levels, without complications. Atrial flutter reverted to sinus rhythm in 98% of the procedures, and atrial fibrillation in 97%. Elective cardioversion in patients with atrial fibrillation was achieved with energies of 200 joules in 82% of the procedures (P less than 0.001) and in atrial flutter with 100 joules in 89% of the cases (P less than 0.001). The most frequent complications were atrial and junctional premature beats in 41% of the cases. We consider this procedure a safe one, effective at the energy levels described, with no need for discontinuation of digitalis therapy, with no mandatory previous anticoagulant therapy, and with no contraindications on pregnancy or implanted pacemakers.