BACKGROUND: The number of people eighty years of age and older in developed countries is increasing, with a concomitant increased demand for total hip replacement. We analyzed the outcomes of total hip arthroplasty for patients in this age group using data from the Finnish National Arthroplasty Registry. METHODS: Data from the Finnish Arthroplasty Registry on 6540 patients (6989 hips) who were eighty years of age or older at the time of a total hip arthroplasty, performed between 1980 and 2004, were evaluated with use of survival analyses. Factors affecting survivorship rates were sought, and the reasons for revision were identified. RESULTS: The mean age of the patients undergoing a primary total hip arthroplasty was 82.7 years. The mean longevity of 3065 patients who died following total hip arthroplasty was 5.1 years. With revision total hip arthroplasty for any reason as the end point, Kaplan Meier survivorship was 97% (95% confidence interval, 96% to 97%) at five years (2617 hips) and 94% (95% confidence interval, 93% to 95%) at ten years (532 hips). Of the 195 hip replacements that required revision, 183 had information on the reason for revision. Eighty-four (46%) were revised for aseptic loosening; thirty-six (20%), for recurrent dislocation; twenty-four (13%), for a periprosthetic fracture; and twenty-three (13%), for infection. Seven hundred and twenty-nine patients had undergone hybrid fixation (a cemented stem and a cementless cup). The survivorship of these replacements was significantly better than that for replacements with cementless fixation in 399 patients (p < 0.05). CONCLUSIONS: In patients who had a total hip arthroplasty when they were more than eighty years old, the prevalence of aseptic loosening was less than that encountered in younger patients, but recurrent dislocation, periprosthetic fracture, and infection were more common in this age group. Cementation of the femoral stem demonstrated better long-term results than cementless fixation, indicating that it may provide better initial fixation and, therefore, longer life-in-service.