This paper describes 2 cases of tricuspid valvular dysplasia (TVD) associated with aortic stenosis and mitral incompetence in newborns. Mitral regurgitation was due to dysplasia, which resembles its tricuspid counterpart and should be termed 'mitral valve dysplasia'. This association of tricuspid and mitral valve dysplasia has been reported only once before. The concomitance of mitral and tricuspid incompetence is noteworthy, since mitral regurgitation can produce left heart failure and mask tricuspid valve disease.