Background and Objectives The optimal transfusion strategy in hip arthroplasty remains controversial despite existing guidelines. The aim of this study was to evaluate the transfusion practice in patients undergoing primary total hip arthroplasty (THA) or revision total hip arthroplasty (RTHA) in Denmark. Materials and Methods We performed a retrospective cohort study of all patients undergoing THA or RTHA in Denmark in 2008. Primary outcomes were intercentre variation in red blood cell (RBC) transfusion rates and the timing of transfusion related to surgery. Results Six thousand nine hundred thirty-two THA patients and 1132 RTHA patients were included for analysis of which 1674 (24%) THA and 689 (61%) RTHA patients received RBC transfusion. Of these, 47% of THA and 73% of RTHA patients received transfusion on the day of surgery. Transfusion rates between centres varied from 7 to 71% and between 26 and 85% in THA and RTHA patients, respectively. Patients receiving RBC transfusion had longer length of stay and for THA patients an increased odds-ratio (5·5) of death within 90 days. Conclusion Despite established guidelines, RBC transfusion practice in hip arthroplasty remains highly variable between Danish hospitals. The effect of RBC transfusion on outcome after hip arthroplasty should be established in prospective randomized controlled trials.