AbstractIn the absence of curative therapy, and with treatment difficult and only partially successful, prevention plays a particularly important role in mental retardation. Research conducted during the past 40 years has identified new causes of mental retardation, new means of early diagnosis, and new ways of prevention. Prenatal diagnosis, newborn screening, dietary supplementation or restriction, hormone replacement, vaccination, and immunotherapy are just some of the techniques that have been applied to prevent mental retardation. Together, these interventions have slightly reduced the overall prevalence of mental retardation, and in some instances have nearly eliminated specific causes. Much remains to be done, including developing better means of early intervention for sociocultural mental retardation and convincing society of the value of investment in such approaches. In addition to these approaches, the research frontiers today are neurobiology, earlier prenatal diagnosis, fetal therapy, gene therapy, and reducing premature birth. The potential of these investigations makes the frontier of prevention research in mental retardation an exciting place to be. MRDD Research Reviews 1998;4:50–58. Published 1998 Wiley‐Liss,