Childhood maltreatment has been implicated as a risk factor for adult obesity. We describe the first prospective assessment of adult obesity in individuals with documented histories of childhood physical and sexual abuse and neglect and a matched comparison group in a 30-year follow-up. Using a prospective cohort design, children with court substantiated cases of physical and sexual abuse and neglect (ages 0–11 years) from a Midwest county during 1967–1971 (n = 410) were matched with children without histories of abuse or neglect on age, sex, race/ethnicity and approximate family social class (n = 303) and followed up and assessed at mean age 41. Outcome measures include BMI and obesity assessed in 2003–2004 as part of a medical status examination and interview. Childhood physical abuse predicted significantly higher BMI scores in adulthood (β = 0.14, P < 0.05), even controlling for demographic characteristics, cigarette smoking, and alcohol consumption (β = 0.16, P < 0.01). Childhood sexual abuse (β = 0.07, not significant) and neglect (β = 0.02, not significant) were not significant predictors of adult BMI scores. These results demonstrate the long-term impact of childhood physical abuse on weight into adulthood and suggest that physically abused children may be at risk for other adverse health outcomes associated with increased weight. Health professionals need to understand this risk for physically abused children and researchers should identify and evaluate strategies for effective interventions.