Transfusion-related acute lung injury is suggested to be a "2-hit" event resulting from priming and activation of pulmonary neutrophils. Activation may result from infusion of lysophosphatidylcholines (LysoPCs), which accumulate during storage of blood products. In the present study, we developed a syngeneic in vivo transfusion model to test whether storage of platelet concentrates (PLTs) results in lung injury in healthy rats as well as in a "2-hit" model using lipopolysaccharide-pretreated rats. In addition, the effect of washing of platelets was studied. In healthy rats, transfusion of aged PLTs caused mild lung inflammation. In LPS-pretreated rats, transfusion of aged PLTs, but not fresh PLTs, augmented pulmonary systemic coagulopathy. When PLTs components were transfused separately, supernatant of aged PLTs, but not washed aged platelets, induced pulmonary injury in the "2-hit" model. Supernatants of aged PLTs contained increased concentrations of LysoPCs compared with fresh PLTs, which enhanced neutrophil priming activity in vitro. We conclude that transfusion of aged PLTs induces lung inflammation in healthy rats. In a "2-hit" model, aged PLTs contribute to pulmonary and systemic coagulopathy, which may be mediated by LysoPCs, which accumulate in the supernatant of PLTs during storage.