Two extremely rare cases of adults with univentricular hearts of right ventricular morphology are presented. Pathogenesis and pathophysiology of univentricular circulation as well as anatomic variants, short information on prognosis and management are briefly discussed. Echocardiographic diagnosis of univentricular heart is described. The first case was a 23-year-old housewife with univentricular heart, functionally common atrium, single atrio-ventricular valve of tricuspid morphology, transposition of great arteries and significant subvalvular pulmonary stenosis. The second case was a 19-year-old student with univentricular heart with moderately depressed systolic function, common atrium, single atrio-ventricular valve of tricuspid morphology, mitral atresia, and non-communication residual left ventricle. Both patients led a normal life with little to moderate limitations of everyday activity.