Congenital Malformations, once considered as rare curiosities of medicine, have been recognized in recent years as an important source of human morbidity and mortality. Consequently, investigators in many medical fields have shown an increasing interest in questions concerned with the etiology and morphogenesis of congenital malformations. The science of teratology which had been neglected somewhat during the last few decades by the medical profession has been revived as a branch of medicine. Yet communications between teratologists working in the basic sciences and those interested in clinical problems of congenital malformations have not been good, and it appeared that a real need existed for a conference in which teratologists working in different branches of medicine could meet, establish contacts and exchange ideas. Such a conference took place on January 12 and 13, 1956, at the College of Medicine, University of Cincinnati. It was sponsored by the Human Embryology and Development Study Section, Division of Research Grants, National Institutes of Health, and by the Association for the Aid of Crippled Children, New York, New York. From the beginning it was decided to keep the group of participants small and the proceedings informal. Ten of the participants gave 20-minute papers designed to provoke debate. Neither the papers nor the excellent ensuing discussions were recorded, as no plans had been made for publication of the proceedings. However, as the conference progressed, there was an increasing demand for publication of the papers presented and Mr. L. W. Mayo, Doctors J. V. Neel, B. M. Patten, J. G. Wilson and I were charged with the task of exploring the possibilities of bringing the proceedings before a larger medical forum.