The rare and curious congenital malformation of the tricuspid valve known as Ebstein's disease or Ebstein's anomaly has been a subject of considerable interest to the cardiologist and the morphologist since its first description by Wilhelm Ebstein in 1866. With the evolution of various surgical techniques for the correction of this anomaly, a thorough understanding of the pathologic anatomy of the malformation assumes greater practical importance. It is now clear that although all hearts with Ebstein's anomaly have in common displaced basal insertions of the septal and posterior leaflets of the tricuspid valve, each case may be pathologically and hemodynamically unique. The malformed tricuspid valve may be incompetent, stenotic, or rarely, imperforate. It may be found in a left-sided tricuspid valve with inversion of ventricles. It is important that these individual variations be recognized so that the operative approach can be tailored to the particular variant of the malformation at hand.