Efforts to prevent mental retardation have been encumbered by lack of scientific and technical knowledge, vague understanding of incidence and prevalence, and scarcity of resources to implement effective public policies. Scientific and social progress toward prevention has pursued a wavelike, erratic course, driven primarily by prevailing social, political, and economic climates and values. The new morbidity model of mental retardation focuses on mental retardation as a symptom or an outcome of underlying biological and social causes. Two primary associates of subsequent morbidity are poverty and low birthweight. Prenatal care is a major factor in improving pregnancy outcome and lowering incidence of low birthweight and prematurity. Access to basic services should be assured, including: prenatal, delivery, and postnatal care; comprehensive care through age 5; and family planning services. Another health problem which is impacted by socioeconomic disadvantage is pediatric acquired immune deficiency syndrome. Problems associated with the new morbidity have human and economic costs which far outweigh the costs of investing time and resources in research, treatment, and prevention. (JDD)