The authors report a case of double-orifice mitral valve (DOMV) which showed mitral stenosis and mild insufficiency. An associated anomaly was secundum atrial septal defect. DOMV is an unusual congenital heart defect. The occurrence of this anomaly with or without secundum atrial septal defect is very rare. More often it is associated with other congenital malformations arising from atrioventricular canal defects. There may be no haemodynamic consequences but mitral insufficiency and/or stenosis may complicate this malformation. Treatment can be summarised as abstention, surgical repair or valve replacement.