The present study was based on data from a longitudinal research program which consisted of 12,032 children, born in the Stockholm area in 1953 of which there were 494 children born with low birth weight (LBW, 2500 g or less). For all children at age 16 it was apparent that adjustment and psychiatric disturbances as well as juvenile delinquency were not related to birth weight and gestational age. LBW girls born at term, had significantly lower school grades, at age 16, than NBW (normal birth weight) girls. NBW boys born pre-term had lower school grades than NBW boys born at term. It is suggested that childhood development is gender related; in girls the birth weight--and in boys the length of the pregnancy was related to school marks at age 16. For boys at 18 years of age at the military draft, it was shown that LBW boys had smaller body size and lower IQ-test scores as compared to NBW boys. Additionally the length of the pregnancy was related to some measures of body size but not to IQ-test scores.