Fractures of the posterior wall are the most common of the acetabular fractures. The aim of this study was to assess the medium-term results of reconstruction of comminuted posterior wall fractures of the acetabulum by using the buttress technique. This is a retrospective review conducted at a level 1 trauma centre. Thirty-two patients (25 men, 7 women, mean age 41 years, range 14–80 years) with comminuted posterior wall fracture of the acetabulum underwent reconstruction of the posterior wall during the period of July 1998 to February 2004. The average follow-up was 43 months (range 24–70 months). Clinical evaluation was based on modified Merle d’Aubigne and Postel scoring. Radiographic evaluation was according to criteria developed by Matta. The postoperative reduction was graded as anatomical in 28 patients (88%) and imperfect in 4 patients (12%). The clinical outcome was excellent in 11 (34% ), very good in 9 (28%), good in 4 (12%), fair in 3 (9%) and poor in 5 (15%). Radiological grading at the final follow-up was excellent 12 (37%), good 11 (34%), fair 4 (12%) and poor 5 (15%). Reconstruction of comminuted posterior wall acetabular fractures by buttress technique can be expected to produce good results. It can provide a stable fixation of the posterior wall amenable to early range of motion and weight bearing.