This paper synthesizes findings of major research studies on development of learning impairment and its prevention in children from birth to age 5. The paper's scope does not include children who died or suffered major retardation. The paper attempts to demystify the language of research and medicine to clarify the prevalence of health, environmental, and poverty-based risk factors; their impact on a child's ability; and ways to prevent the risk factor or ameliorate the learning impairment once it occurs. Major preventable factors associated with learning impairment are low birthweight, prenatal alcohol exposure, maternal smoking, prenatal exposure to drugs, lead poisoning, child abuse and neglect, and malnutrition: each of these factors is discussed in turn. Prevention strategies include, among others, access for all women to early and informative prenatal care, health care before pregnancy and between pregnancies, developmentally stimulating infant day care with parent involvement, school health education, and societal commitment to diminish poverty. A separately printed 3-page summary is appended. (JDD)