Background: Longitudinal research has produced a wealth of knowledge about individual, family, and social predictors of crime. However, nearly all studies have started after children are age 5, and little is known about earlier risk factors. Methods: The 1970 British Cohort Study is a prospective population survey of more than 16,000 children born in 1970. Pregnancy, birth, child, parent, and socioeconomic characteristics were measured from medical records, parent interviews, and child assessments at birth and age 5. Conduct problems were reported by parents at age 10, and criminal convictions were self-reported by study members at ages 30-34. Results: Early (up to age 5) psychosocial risk factors were strong predictors of conduct problems and criminal conviction. Among pregnancy and birth measures, only prenatal maternal smoking was strongly predictive. Risk factors were similar for girls and boys. Additive risk scores predicted antisocial behaviour quite strongly. Conclusions: Risk factors from pregnancy to age 5 are quite strong predictors of conduct problems and crime. New risk assessment tools could be developed to identify young children at high risk for later antisocial behaviour.