Among the congenital anomalies associated with tetralogy of Fallot, tricuspid insufficiency is rare. In two children with tetralogy of Fallot associated with congenital tricuspid insufficiency, one due to elongation of the anterior papillary muscle and resultant redundancy of the anterior cusp of the tricuspid valve and another due to dysplasia of the tricuspid valve, both tetralogy of Fallot and tricuspid insufficiency were corrected simultaneously with success. The etiologic factors, clinical manifestations and surgical implications of this combination of anomalies are discussed. It is emphasized that tricuspid regurgitation must be repaired simultaneously in order to avoid low cardiac output syndrome in the case of tetralogy of Fallot associated with tricuspid regurgitation, particularly in which pulmonary regurgitation might occur after relief of the outflow tract obstruction.