['Although the benefits of acute stabilization of long bone fractures are recognized, the role of early fixation of unstable pelvis and acetabular fractures is not well-defined. The purpose of this study was to review complications and hospital course of patients treated surgically for pelvis and acetabulum fractures. We hypothesized that early definitive fixation would reduce morbidity and decrease length of stay.', 'Six hundred forty-five patients were treated surgically at a level I trauma center for unstable fractures of the pelvic ring (n = 251), acetabulum (n = 359), or both (n = 40). Mean age was 40.5 years, and mean Injury Severity Score (ISS) was 25.6 (range 9-66). They were retrospectively reviewed to determine complications including acute respiratory distress syndrome (ARDS), pneumonia, deep vein thrombosis, pulmonary embolism, multiple organ failure (MOF), infections, and reperations.', 'Definitive fixation was within 24 hours of injury in 233 patients (early, mean 13.4 hours) and >24 hours in 412 (late, mean 99.2 hours). Twenty-nine patients (12.4%) had complications after early fixation versus 81 (19.7%) after late, p = 0.006. Length of stay and intensive care unit days were 10.7 days versus 11.6 days (p = 0.26) and 8.1 days versus 9.9 days (p = 0.03) for early and late groups, respectively. With ISS >18 (n = 165 early [ISS 32.7]; n = 253 late [ISS 33.1]), early fixation resulted in fewer pulmonary complications (12.7% versus 25%, p = 0.0002), less ARDS (4.8% versus 12.6%, p = 0.019), and less MOF (1.8% versus 4.3%, p = 0.40). Rates of complications, pulmonary complications, deep vein thrombosis, and MOF were no different for patients with pelvis versus acetabulum fractures. In patients receiving ≥ 10U packed red blood cells (n = 41 early, n = 56 late) early fixation led to fewer pulmonary complications (24% versus 55%, p = 0.002), less ARDS (12% versus 25%, p = 0.09), and MOF (7.3% versus 14%, p = 0.23). Two hundred ten patients had some chest injury (32.6%). Chest injury with Abbreviated Injury Scores ≥ 3 was present in 46 (19.7%) of early and 78 (18.9%) of late patients (p = 0.44) and was associated with pulmonary complications in 26.1% versus 35.9%; ARDS in 15.2% versus 23.1%; and MOF in 6.5% versus 6.4%, respectively (all p > 0.20). However, chest injury with Abbreviated Injury Scores ≥ 3 was independently associated with more complications including ARDS (20.2% versus 3.3%, p < 0.0001), other pulmonary complications (32.3% versus 10.4%, p < 0.0001), and MOF (6.5% versus 1.2%, p = 0.0016), regardless of timing of fixation.'] Does early definitive stabilization of unstable pelvis and acetabulum fractures reduce morbidity?