A two-day-old baby with a type-I truncus arteriosus and double mitral valve orifice is reported. The double mitral valve orifice and additional lesions of each subdivision of the mitral valve were clearly shown by two-dimensional echocardiography. The medial orifice had a cleft leaflet and the lateral one a parachute-like disposition of the tension apparatus. This is the first report of double mitral valve orifice associated with truncus arteriosus, and the first in which anomalies of the subdivisions of the mitral valve were detected by two-dimensional echocardiography.