This chapter summarizes how prevention, diagnosis and services can result from the activities of a research programme on the group of rare diseases constituted by congenital anomalies. The Spanish Collaborative Study of Congenital Malformations (ECEMC) is a research programme based on a case-control registry of consecutive newborn infants with congenital anomalies. Its aim is the prevention of this group of rare diseases, through the research on their causes and pathogenesis, combined with the translational activity to transfer the benefits of this knowledge to the general population and health care providers. Its experience could be applied to the research on other rare diseases. The different levels of prevention (primary, secondary, tertiary and quaternary) are briefly defined, and the way in which these levels are being applied or can be applied to congenital defects prevention is reviewed. The main primary prevention measures regarding congenital anomalies are also detailed. To this respect, the benefits derived from the activity of Teratology Information Services (TIS), for the general population as well as for health care providers, are explained. It is finally emphasized how the epidemiological data can contribute to the prevention of that group of rare diseases.