A retrospective study was done on 14 cats and 36 dogs diagnosed with right atrioventricular valve malformations (RAVM), either tricuspid dysplasia (n = 38) or Ebstein's anomaly (n = 12). Comparison with a large reference population including 85 250 animals allowed an epidemiologic analysis of these RAVM, demonstrating that Labrador, Boxer and Chartreux cats had a 35, 7 and 11-fold higher risk respectively to be affected by one of these heart diseases than other breeds, without sexual predisposition. In 93% of cases, cardiac auscultation revealed a heart murmur, whose grade was not significantly correlated with the echographic stages of the valvular disease. The echocardiographic examination confirmed the frequent association between RAVM and other congenital anomalies, particularly mitral dysplasia, in 84% and 20% of tricuspid dysplasia and Ebstein anomaly respectively. Last, the prognosis of RAVM was worsened by atrial fibrillation and right-sided heart failure.