Atrioventricular canal is divided into incomplete, intermediate and complete types. In ostium primum ASD [incomplete type] mitral valve cleft is almost always present, but ostium primum ASD with tricuspid valve cleft is a rare congenital anomaly. The patient was a 7 year old female whose complains were palpitation, exertional dyspnea and growth retardation. The chest films showed moderate cardiomegaly [C-T ratio, 61%]. EKG, Echocardiography, cardiac catheterization and left ventriculography were performed. Open heart surgery was done under the impression of incomplete atrioventricular canal. At the time of operation, ostium primum ASD [2x2.5 cm in diameter], secundum type ASD [lxl.5 cm in diameter] and cleft in the septal leaflet of the tricuspid valve were noted. But mitral valve was normal without cleft and VSD was not noted. Each anomalous portion was repaired. The patient made an uneventful recovery and we report this case, review and discuss the literatures.