BACKGROUND: Biventricular pacing improves the clinical status and ventricular function in patients with congestive heart failure (CHF) and intraventricular conduction delay. However, patient selection criteria including NYHA functional class, rhythm, PR interval, QRS duration (QRSd), left ventricular ejection fraction (LVEF), left ventricular diastolic diameter (LVDD), and other variables are not clearly defined. OBJECTIVE: To determine which and how many patients referred for an initial cardiac transplantation evaluation may be eligible for biventricular pacing (BP) according to the criteria of recently completed trials of cardiac resynchronization therapy (CRT). METHODS: This was a retrospective review of 200 patients, whose mean age was 51 +/- 13 years (173 men). Sinus rhythm was present in 88% of the patients, 107 had a QRSd > 120 ms, and 38% had left bundle branch block. LVDD was 72.5 +/- 12 mm and LVEF 21.7 +/- 9.3%; 54% had mitral regurgitation. RESULTS: When NYHA class, electrocardiographic, and ventricular function criteria were considered separately, a high proportion of patients appeared to be candidates for CRT: 70.5% were in NYHA functional class III/IV, 34% had QRSd > or = 150 ms, 60% had LVDD > or = 60 mm and 53.5% LVEF < or = 35%. However, the proportions of patients eligible for CRT were different according to the selection criteria of recently completed trials: 18% of the patients with InSync criteria, 13% of the patients with MUSTIC SR criteria, 0.5% with MUSTIC AF criteria, 27% of patients with MIRACLE criteria, and 35% of the patients with CONTAK CD criteria (without considering indications for implantable cardioverter defibrillator). CONCLUSION: In this population-based study, a wide range of patients (13% to 35%) would have been candidates for CRT, according to the selection criteria of different completed trials.