We analyzed the temporal changes in the caseload of primary and revision hip and knee arthroplasty surgeons in the United States between 1990 and 2004. The Nationwide Inpatient Sample was used to identify arthroplasty procedures and the surgeons who performed them. Annual caseloads were analyzed for each procedure; 47% +/- 2% and 39% +/- 2% of hip and knee surgeons performed revisions nationwide. Average revision caseloads increased slightly over time at a rate of 1.2 and 1.4 cases per surgeon per decade for total hip arthroplasty (THA) and total knee arthroplasty (TKA), respectively. The caseload of primary THA and TKA increased by 1.4 and 1.7 cases per surgeon per decade. The caseload for the top 5% of primary THA and TKA surgeons increased from 25 to 45 and 33 to 86, respectively, during this period compared with the median caseload, which increased from 4 to 5 (hip) and 5 to 10 (knee). The revision caseload of surgeons has increased over time, particularly for surgeons with the highest caseloads.