Objective To examine racial–ethnic differences in asthma controller medication use among insured U.S. children. Data Sources Linked nationally representative data from the Medical Expenditure Panel Survey (2005–2008), the 2000 Decennial Census, and the National Health Interview Survey (2004–2007). Study Design The study quantifies the portion of racial–ethnic differences in children's controller use that are attributable to differences in need, enabling and predisposing characteristics. Principal Findings Non‐Hispanic black and Hispanic children were less likely to use controllers than non‐Hispanic white children. Blinder‐Oaxaca decomposition results indicated that observable characteristics explain less than 40 percent of the overall differential in controller use between non‐Hispanic whites and non‐Hispanic blacks. In contrast, observable characteristics explain more than two‐thirds (71.3 percent) of the overall non‐Hispanic white‐Hispanic differential in controller use. For non‐Hispanic blacks, a majority of the explained differential in controller use were attributed to enabling characteristics. For Hispanics, a significant portion of the explained differential in controller use was attributed to predisposing characteristics. In addition, a larger portion of the differential in controller use was explained by observable characteristics for publicly insured non‐Hispanic black and Hispanic children. Conclusions The large observed differences in controller use highlight the continuing challenges of ensuring that all U.S. children have access to quality asthma care.