The displaced femoral neck fracture remains a major challenge to orthopedic surgeons, as the elderly population is increasing. Elderly patients with femoral neck fractures often have other medical conditions, fragile bones, and poor compliance. Thus, for elderly patients who need early ambulation and funtional recovery, bipolar prosthesis is accepted as an appropriate treatment. We report a study of 58 cases of bipolar hemiarthroplasty with a femoral neck fracture and a physiologic age older than 65 years from January 1991 to May 1996. The purpose of this study is to evaluate the functional outcome of bipolar hemiarthroplasty and correlation between preoperative medical conditions and Harris hip score in femoral neck fractures in the elderly patients. The results obtained were as followings. 1. 90% of patients had uncontrolled medical conditions. Cardiovascular and pulmonary disease were main preexisting medical conditions. 2. The preoperative medical conditions were important deteminants for the functional results after bipolar hemiarthroplasty. 3. Dislocated bipolar prosthesis needed open reduction or revision to total hip arthroplast due to disassembly of the prosthesis caused by attempted closed reduction.