Tricuspid valve dysplasia was diagnosed in 2 month-old german shepherd dog. Radiographic and echocardiographic examination was performed and they revealed severe dilatation of the right atrium, dilatation of the right ventricle, and septal leaflet tethered to the right side of the septum. On Doppler echocardiography, tricuspid valve incompetence was detected, flow velocity ranging from 3-4 m/sec. Color Doppler examination showed large turbulent jet in the right atrium.