Using data on 4,813 children from the ALSPAC cohort in Bristol, United Kingdom, recontacted in 1998–1999, the authors investigated whether intrauterine growth restriction (indexed by birth weight and length) was associated with behavioral problems at age 7 years. Childhood behavioral problems were measured by using a brief behavioral screening questionnaire (the Strengths and Difficulties Questionnaire (parental completion)). For term singleton infants, a one standard deviation increase in birth weight was associated with an 11% reduction in the odds of behavioral problems at age 81 months. After adjustment for confounders and birth length, this association was no longer seen. The association with birth length remained after adjustment for confounders. A one standard deviation increase in birth length was associated with a 14% decrease in the odds of being in the top tertile of total behavioral difficulties at age 81 months (odds ratio=0.86, 95% confidence interval: 0.79, 0.95) and was similarly associated with hyperactivity and conduct problems. Evidence was weak for an association between birth length and behavioral problems earlier in childhood. In summary, there was a weak association between intrauterine growth restriction, indexed by birth length (rather than weight), and childhood behavioral problems. Future work should focus on elucidating the biologic mechanisms that lead to variations in birth length and underlie this association.