OBJECTIVES: Transfusion-Related Acute Lung Injury (TRALI) is a serious transfusion complication resulting in pulmonary edema and respiratory failure. The study objectives were to assess TRALI occurrence and potential risk factors among inpatient Medicaid beneficiaries under 65 years of age, during 2007-2010. METHODS: This retrospective claims-based study utilized large Medicaid databases. Transfusions were identified by recorded procedure and revenue center codes, while TRALI was ascertained via ICD-9-CM diagnosis code. Revenue center units were used to quantify blood use. Study evaluated TRALI rates (per 100,000 transfusion stays) among Medicaid beneficiaries, overall and by year, age, sex, race, number of units and blood components transfused. RESULTS: Of 1,123,113 inpatient transfusion stays for Medicaid beneficiaries during 2007-2010, 162 had TRALI diagnosis recorded, an overall rate of 14.42 per 100,000 stays. Annual TRALI rates were 12.70, 10.67, 16.60, and 18.14, respectively. TRALI rates for ages 0-9, 10-19, 20-29, 30-39, 40-49, 50-59, and 60-64 were 5.15, 13.41, 17.22, 19.59, 19.44, 13.66, and 10.54. Rates for females and males were 12.78 and 17.28, whereas for whites and non-whites were 15.55 and 13.45. TRALI rates by number of units were: 9.56 for 1 unit, 7.72 for 2-4 units, 17.70 for 5-9 units, and 62.12 for >9 units. Rates by blood component groups were: 13.86 for RBCs only, 4.93 for plasma only, 23.22 for platelets only, 37.37 for platelets and plasma, 56.02 for RBCs and plasma, 43.12 for RBCs and platelets, and 74.75 for RBCs, plasma, and platelets. CONCLUSIONS: This is the first and largest-to-date claims-based TRALI study among Medicaid beneficiaries. The results show a possible trend of increasing TRALI occurrence over time. The findings also suggest that TRALI rates vary by age, sex, race, number of units, and blood components transfused, with highest rates for stays with >9 units transfused and for stays with RBCs transfused in combination with plasma and platelets.