Intraventricular resynchronization with pacemakers is a promising therapy for patients with refractory cardiac failure and intraventricular conductions delay. However its long term effects are not well known. Aim: To report the results of this therapy in patients with cardiac failure. Patients and methods: Fourteen patients (11 male), whose mean age was 68 years, with a severe and refractory cardiac failure, have been treated in our unit using intraventricular resynchronization with pacemakers. Eight had a coronary heart disease and six a dilated myocardiopathy. The pacemaker was implanted transvenously, with conventional stimulation in atrium and right ventricle. The left ventricle was stimulated through an epicardial vein, accessed through the coronary sinus. Results: In one patient the high thresholds did not allow a left ventricular stimulation. In the other 13 patients, a clinical improvement was observed in 11 (85%), that has been sustained for a mean of 8.2 months. The ejection fraction improved form 23.5 to 32.4% (p <0.001), the 6 min walking test improved from 347 to 437 m (p=0.003) and the functional capacity changes from 3.3 to 2.7 (p <0.001). Three patients died during follow up. One was the patient in whom the stimulation failed and two had a sudden death. No complications of the procedure were observed. Conclusions: In this series, intraventricular resynchronization with pacemakers was effective in 11 of 13 patients, improving functional capacity and ejection fraction. Sudden death could be avoided adding a defibrillator to the pacemaker system (Rev Méd Chile 2003; 131: 1101-10)