This study tests the feasibility of using an integrated state agency administrative database to identify social complexity risk factors and examined their relationship to emergency department (ED) use. A retrospective cohort study among children under age 18 years with state Medicaid insurance coverage was linked to child and parent administrative data to identify a set of social complexity risk factors, such as poverty and parent mental illness, that have either a known or hypothesized association with suboptimal health care use. Nine risk factors were associated with a higher rate of ED use. The rate increased as the number of risk factors increased from 0 to 5 or more, reaching about twice the rate when 5 or more risk factors were present in children aged younger than 5 years and in children aged 5 to 17 years.