Effects of right bundle branch block on hemodynamics of lesser circulation and pulmonary blood flow were studied with analysis of phasic structure of right ventricular systole and indices of specific contractility and disextensibility of cardiac chambers, mean pulmonary pressure, total pulmonary and peripheral vascular resistances. A correlation was found between phasic structure of right ventricular systole and duration of right ventricular complex. Hemodynamic changes were more pronounced when complete right bundle branch block was combined with right ventricular hypertrophy.