BACKGROUND The majority (86%) of THAs performed in the United States are uncemented. This may increase the revision burden if uncemented fixation is associated with a higher risk of revision than other approaches. QUESTION/PURPOSES We sought to investigate trends for use of uncemented fixation and to analyze age-stratified risk of revision comparing cemented, hybrid, and uncemented fixation as reported by national hip arthroplasty registries. METHODS Data were extracted from the annual reports of seven national hip arthroplasty registries; we included all national registries for which annual reports were available in English or a Scandinavian language, if the registry had a history of more than 5 years of data collection. RESULTS Current use of uncemented fixation in primary THAs varies between 15% in Sweden and 82% in Canada. From 2006 to 2010 the registries of all countries reported overall increases in the use of uncemented fixation; Sweden reported the smallest absolute increase (from 10% to 15%), and Denmark reported the greatest absolute increase (from 47% to 68%). Looking only at the oldest age groups, use of uncemented fixation also was increasing during the period. In the oldest age group of each of the registries we surveyed (age older than 65 years for England-Wales; age older than 75 years in three registries), cemented fixation was associated with a lower risk of revision than was uncemented fixation. CONCLUSIONS Increasing use of uncemented fixation in THA is a worldwide phenomenon. This trend is paradoxic, given that registry data, which represent nationwide THA outcomes, suggest that cemented fixation in patients older than 75 years results in the lowest risk of revision. LEVEL OF EVIDENCE Level II, systematic review. See Guidelines for Authors for a complete description of levels of evidence.