This monograph, which reports findings from the New Jersey Governor's Council on the Prevention of Mental Retardation, discusses the scope of mental retardation (MR), its causes, identification of people at risk, and prevention methods. The Council cites several cost-effective prevention programs, such as vaccination programs and prenatal care services. Council recommendations to prevent MR before conception and during pregnancy include: counseling for genetic and teratologic defects, developing information on exposure to environmental contaminants, educating persons at risk about alcohol and the unborn, fostering new attitudes about substance abuse, reducing the risk of adolescent pregnancy, and insuring the medically needy. To prevent MR at the time of birth, the Council recommends ensuring full-term births and providing follow-up care for infants with birth defects and infants at risk. Recommendations for MR prevention during childhood include: immunizing against infectious diseases, expanding health services in school settings, encouraging breast feeding, expanding the Special Supplemental Food Program for Women, Infants and Children, providing for public health nutritionists, testing for lead poisoning, teaching parenting skills, improving protection in automobiles and school buses, and creating an Office for Prevention Programs. Numerous statistical tables, some specific to New Jersey and others nationwide in scope, are incorporated throughout the text. (JDD)