Since research is concentrated to a large extent on patients with left bundle branch block, we aimed at evaluating the hypothesis that measurements of certain intervals and other characteristics of the ECG may change over time in patients with right bundle branch block(RBBB), and to design a model, which could be implemented in research and clinical practice, irrespective of the specific ECG features present. The duration of the QRS complex, QT, QTc, and PR intervals, the frontal QRS axis, the heart rate and the presence of hemiblocks, atrioventricular blocks, and atrial fibrillation were compared in the 1st and last of all available ECGs for each patient. Also, a subgroup of patients who had a ventricular aneurysm(VA) was compared with the remaining patients, with respect to the above variables. This longitudinal analysis included all of the patients with RBBB followed in our Cardiology Clinic. There were no significant changes in the ECG variables from the two ECGs recorded 487.6± 410.1(range 0- 1,476) days apart, in the two comparisons carried out in 151 patients with RBBB. Comparison of the above- described ECG intervals and characteristics of patients with RBBB were found to be stable over the time course of the investigation. This methodological study is presented as a model to be used serially and prospectively in research and clinical practice for the follow- up of patients with bundle branch block, VA, dilated cardiomyopathy, congestive heart failure, or those considered for cardiac resynchronization therapy. Since research is concentrated to a large extent on patients with left bundle branch block, we aimed at evaluating the hypothesis that measurements of certain intervals and other characteristics of the ECG may change over time in patients with right bundle branch block (RBBB), and to design a model, which could be implemented in research and clinical practice, irrespective of the specific ECG features present. The duration of the QRS complex, QT, QTc, and PR intervals, the frontal QRS axis, the heart rate and the presence of hemiblocks , atrioventricular blocks, and atrial fibrillation were compared in the 1st and last of all available ECGs for each patient. Also, a subgroup of patients who had a ventricular aneurysm (VA) was compared with the remaining patients, with respect to the above variables. This longitudinal analysis included all of the patients with RBBB followed in our Cardiology Clinic. There were no significant changes in the ECG variables from the two ECGs recorded 487.6 ± 4 10.1 (range 0 - 1,476) days apart, in the two comparisons carried out in 151 patients with RBBB. Comparison of the above- described ECG intervals and characteristics of patients with RBBB were found to be stable over the time course of the investigation. methodological study is presented as a model to be used serially and prospectively in research and clinical practice for the follow-up of patients with bundle branch block, VA, dilated cardiomyopathy, congestive heart failure, or those considered for cardiac resynchronization therapy.