Aims: Our study was designed to compare a series of elderly individuals who sustained a displaced femoral neck fractures treated with either a bipolar prosthesis or a modular unipolar prosthesis. Methods: In a level I orthopaedic trauma center, 140 from 234 consecutive patients with displaced intracapsular fractures of the proximal femur (Garden Types III-IV) underwent primary prosthetic replacement. 122 of them received a bipolar prosthesis (68 patients 55.7%) or a modular unipolar prosthesis (54 patients Ð 44.3%). The mean age was 62 years. Results: 24 patients died during the period of study and 32 patients were lost to follow-up. Consequently, 66 patients were followed for a minimum 18 months: 34 in the bipolar prosthesis group and 32 in the modular unipolar prosthesis group. Functional status of the hip was compared between both groups, as well as the incidence of complications or need for revision surgery. No signiþcant differences were found between the bipolar and unipolar group. Conclusions: Either bipolar or modular unipolar hemiarthroplasty may be offered as alternative treatments for a displaced intracapsular fracture of the proximal femur in elderly patients. The incidence of the acetabular erosion in the unipolar group may demonstrate the theoretical beneþt of the bipolar prosthesis, although the differences were not statistically signiþcant.