This study examined retrospectively the clinical and radiographic features of acute displaced acetabular fractures which heavily influence the quality of an open reduction and clinical outcome. Of 424 acute fractures (119 simple and 305 associated injuries) in 411 patients, the mean time from the injury to surgery was 8.2 days (range, 0-21 days). The mean age of the patients was 46.5 years (range, 13-89 years), and followup was an average of 9.3 years (range, 3-21 years). For the 424 hips, the reduction was anatomic in 282 (67%), imperfect in 90 (21%), poor in 39 (9%), and secondarily congruent in 13 both-column fractures (3%). The quality of the reductions markedly deteriorated with advancing age. Clinically, the Harris hip score was excellent in 179 (42%), good in 126 (30%), fair in 54 (13%), and poor in 65 (15%). Excellent or good clinical outcomes were recorded in 249 of 282 patients (89%) with an anatomic reduction. Of the 119 patients with fair and poor results, 92 patients (77%) had complicating factors recognizable at clinical presentation, including extensive impaction, articular abrasion, a femoral head or neck fracture, or endogenous obesity. Although stable anatomic reduction of most displaced acetabular fractures affords the optimal prognosis, especially in younger patients, the initial clinical and radiologic evaluations delineate a sizable minority with poorly prognostic features that favor a poor clinical outcome after internal fixation, by minimizing the likelihood for an anatomic reduction or compromising the outcome despite an anatomic reduction. With the rapidly aging population accentuating this trend, a reappraisal for the role of the current therapeutic alternatives of nonoperative treatment, a limited open reduction, or an acute total hip replacement merits review.