Between June 1989 and May 1995, the authors surgically treated 64 patients with unstable posterior pelvic in juries. Fracture types included Tile Type C1 (75%), C2 (8%), and C3 (17%). There were 19 sacroiliac dislocations, 12 sacral fractures, 4 transiliac fractures, and 29 sacroiliac fracture dislocations. Average patient age was 32 years and Injury Severity Score was 27 points. Posterior fixation was accomplished by percutaneous iliosacral screw insertion in 53 patients (83%). Only pure transiliac fractures were treated without iliosacral screws. There were no iatrogenic nerve palsies. During the study, there was increased reliance on internal fixation of the anterior pelvic ring that aided in anatomic alignment of the pelvis for posterior fixation and resulted in decreased chronic pubic tenderness. The use of external fixation for definitive treatment was abandoned. Patients were observed for an average of 36 months (range, 5-74 months). Fifty-two patients were available for recent complete followup. Fifty-one patients (98%) healed their pelvic disruptions; there was 1 sacral nonunion. A 40-point pelvic outcome grading scale was developed based on physical examination, pain, radiographic analysis, and activity/work status. Scores obtained by this scale correlated closely with the Short Form-36 Health Survey scores. Patient functional outcome after posterior pelvic fracture was not associated with Injury Severity Score or fracture location.