Childhood injuries lead to increased morbidity and result in significant costs to public insurance programs. People with mental retardation, most of whom are covered by Medicaid, are at high risk for injury, which has implications for community inclusion, a central policy goal. Medicaid data from inpatient, outpatient, and long-term care settings represent an important new resource for injury surveillance in this population. Injury prevalence for 8.4 million Medicaid-eligible children in 26 states was measured using 1999 eligibility and claims data; 36.9% Medicaid beneficiaries ages 1 to 20 with mental retardation had at least one injury claim as compared with 23.5% of those without mental retardation. Prevalence rates are reported by gender and age for a variety of injury types.