Trauma transfusion strategies, which incorporate balanced red-cell concentrate (RCC)-to-fresh frozen plasma (FFP) ratios, may be associated with improved survival in massively transfused patients. However, the use of this approach in nonmassively transfused patients has led to concern regarding an increase in acute respiratory distress syndrome (ARDS). The aim of this study was to assess the incidence of ARDS in transfused UK military casualties. All UK military casualties receiving an RCC transfusion within a 16-month period were identified from the UK Trauma Registry, and chest radiographs retrieved. If bilateral infiltrates were present, case notes were retrieved to calculate the PaO2/FIO2 ratio in accordance with the American-European Consensus Conference criteria. Patients were divided into massively transfused (≥ 10 U/24 h) and nonmassively transfused (<10 U/24 h) receiving a high ratio (≥ 0.75) or low (<0.75) RCC:FFP ratio. The primary outcome was the development of ARDS within 7 days of transfusion. Primary blast lung injury was excluded. Of 145 patients identified, 144 had records available for analysis with a median injury severity score of 21. The majority were injured by explosion (76%), and the remainder by gunshot (24%). There were 60 nonmassively transfused patients with 18 in the low and 42 in the high RCC:FFP ratio groups. Of the remaining 80 massively transfused patients, 11 were in the low and 73 were in the high-ratio groups. There was no difference in the incidence of ARDS between low- and high-ratio groups in either nonmassively transfused (22.2% vs. 9.5%; P = 0.232) or massively transfused (18.2% vs. 23.3%; P = 1.000) casualties. There was no statistically significant increase in the incidence of ARDS in UK casualties treated with high, compared with low, ratios of plasma to RCC.