This paper presents the short term results of an ongoing prospective randomized trial comparing a cemented unipolar with a cemented bipolar hemiarthroplasty for the treatment of displaced femoral neck fractures in the elderly. Forty-seven patients with an average age of 77 years completed 6-month followup. Outcomes at 6 weeks, 3 months and 6 months were assessed by completion of a patient oriented hip outcome instrument and by functional tests of walking speed and endurance. No differences in the postoperative complication rates or lengths of hospitalization were seen between the two groups. Patients treated with a bipolar hemiarthroplasty had greater range of hip motion in rotation and abduction and had faster walking speeds. However, no differences in hip rating outcomes were found. These early results suggest that use of the less expensive unipolar prosthesis for hemiarthroplasty after femoral neck fracture may be justified in the elderly.