Perinatal, growth, social, and psychologic data, collected through seven years of age on 144 adopted children and on 288 matched controls as part of a prospective study of 3,120 children, were subjected to statistical analysis. Only single births and healthy children were included. The adopted subjects were divided into two groups: 94 children who were adopted by nonrelatives (77 prior to one year of age and 17 after one year of age); and 50 children who remained with their biologic mothers and were subsequently adopted by stepfathers. Children who were adopted prior to one year of age had significantly higher IQs at four years of age then did their controls; at seven years of age, however, their IQs were similar even though the adopted children were raised in a higher socioeconomic environment. The adopted children had better academic achievement and were taller at four and seven years of age than were the controls. The performance of the children adopted after one year of age, even though they were raised in a higher socioeconomic environment, were like those of their controls at both four and seven years of age. The performance of the children who remained with their biologic mothers was similar to that of their controls. Maternal intelligence generally did not correlate well with adopted children's intelligence; however, a specific significant positive correlation could be shown between maternal intelligence and the intelligence of children who remained with their biologic mothers.