Anatomic study of 54 autopsied cases of tricuspid atresia revealed mitral valvar anomalies in 9 (16.7%). The morphologic findings in these 9 cases are presented and compared with 45 cases having a normal mitral valvar apparatus. The anomalies included a cleft valve in 2, parachute valve in 2, straddling valve in 3, and a valve with dual orifice in 2.Two of these cases had more than one anomaly. Data from echocardiography and cardiac catheterisation, when available, had failed to diagnose the anomalies during life. The anomalies were more commonly associated with discordant ventriculo-arterial connections (33.3% versus 13.3%, p < 0.01), were associated significantly with a large ventricular septal defect (33.3% versus 4.4%, p < 0.01), and with pulmonary hypertension (33.3% versus 2.2%, p < 0.01). Two of 3 post operative deaths among the 9 were due to hemodynamic consequences arising from the uncorrected mitral valvar anomaly (parachute valve in both ). Diagnosis of these anomalies prior to surgical correction is imperative, as their presence may necessitate repair or replacement of the mitral valve. Failure to do so may result in increased perioperative mortality, congestive cardiac failure and arrhythmias at a later date. Mitral valvar anomalies may be a contributory factor to the early onset of cardiac failure seen in patients with tricuspid atresia undergoing palliative shunts.