Trauma is the leading cause of death in young people. Trauma deaths have a classic trimodal distribution; in late death (3 days to 3 weeks postinjury), infection is the principal cause. Because pneumonia is a major cause of morbidity in trauma patients, early identification of subjects at a high risk of developing nosocomial pneumonia (NP) can reduce morbidity and costs. Methicillin-sensitive Staphylococcus aureus (MSSA) is the predominant pathogen in multiple-trauma patients in coma, and nasal MSSA colonization at time of severe injury may increase the risk of MSSA pneumonia. In the remaining patients, gram-negative bacilli are responsible for the majority of cases. Prolonged mechanical ventilation, continuous enteral feeding, and craniotomy are risk factors for NP in trauma patients. Diagnosis of NP in these patients is difficult because radiographic infiltrates may not highlight any infection. In coma patients, coverage with a beta-lactam active against MSSA is mandatory. Variations in organisms and sensitivities across intensive care units due to differences in demographic characteristics or comorbidities should be considered.