OBJECTIVES: To investigate the incidence and onset time of pneumonia for patients with severe traumatic brain injury (TBI) in the early phase of rehabilitation and to identify parameters associated with the risk of pneumonia. DESIGN: Observational retrospective cohort study. SETTING: Subacute rehabilitation department in a university hospital in Denmark. PARTICIPANTS: Patients (N=173) aged 16 to 65 years with severe TBI who were admitted during a 5-year period. Patients are transferred to the brain injury unit as soon as they ventilate spontaneously. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Pneumonia. RESULTS: Twenty-seven percent of the patients admitted to the brain injury unit were in treatment for pneumonia; pneumonia developed in 12% of the patients during rehabilitation; the condition occurred within 19 days of admission in all but 1 patient. Of these patients, 81% received nothing by mouth. Three factors identified patients at highest risk of pneumonia: Glasgow Coma Scale score less than 9 (1 day after cessation of sedation); Rancho Los Amigos Scale score less than 3 (on admission); and no oral intake on admission. Having a tracheotomy tube and/or feeding tube was also associated with a higher occurrence of pneumonia. CONCLUSIONS: Among patients with severe TBI, 27% had pneumonia at transfer from the intensive care unit. Pneumonia developed in only 12% of the participants during rehabilitation. Patients with a low level of consciousness and patients with a tracheotomy tube or feeding tube had a higher likelihood of pneumonia.