Postoperative femoral periprosthetic fracture is an uncommon complication of total hip arthroplasty surgery, but several centers worldwide have recently reported an increase in total numbers of such fractures. This severe complication is costly for society and results in high morbidity. Our analysis of 1049 periprosthetic fractures occurring in Sweden between 1979 and 2000 and recorded in the Swedish National Hip Arthroplasty Register focuses on patient- and implant-related factors, fracture classification, and fracture frequency. These were our 3 major findings: (1) a majority of the patients who sustained a late periprosthetic femoral fracture had a loose stem. (2) Implant-related factors are significantly associated with occurrence of a periprosthetic fracture. (3) Since the 1980s in Sweden, treatment results for periprosthetic fractures have been poor, with low long-term survivorship and a high frequency of complications. We have initiated further studies of this important problem.