To identify predictors of prolonged (>7 days) mechanical ventilation (MV) in patients with blunt thoracic trauma. Prospective analysis of consecutive patients. Adult intensive care unit (ICU) in a teaching, tertiary-care hospital. Sixty-nine patients (53 men, 16 women) with thoracic trauma having a median age of 35 (range 17-85) years and a median injury severity score (ISS) of 29 (range 14-41) were enrolled in the present study. Associated injuries included head-neck (77%), extremities (72%), external (67%), abdomen-pelvis (67%), and face (55%). Patient surveillance and data collection. Thirty-three (48%) of the 69 patients required prolonged ventilatory support, ranging in duration from 8 to 38 (median 18) days. Logistic regression analysis revealed that advancing age (odds ratio=1.04, p=0.04), severity of head injury (odds ratio=1.92, p=0.008), and bilateral thoracic injuries (odds ratio=12.80, p<0.0001) were significant and independent predictors of long-lasting MV. In contrast, gender, injuries affecting the other body regions (face, abdomen-pelvis, extremities, and external), laparotomy in patients with abdominal injury, or PaO(2)/FIO(2) on admission in the ICU, were unrelated to prolonged MV. In thoracic trauma patients admitted in the ICU, prolonged mechanical ventilation was primarily determined by presence of bilateral chest injuries, age, and degree of neurotrauma. This information may help in planning the long-term care of such patients.