We examined the relationship between hospital case volume and patient outcome (ie, length of hospital stay and hospital charges) for both total hip arthroplasty (THA) and total knee arthroplasty (TKA). The study included 1561 patients who had total joint arthroplasty from April 1, 2001, to March 31, 2003. Using the mean values of THA or TKA surgical case volumes, the participating hospitals were divided into high-volume and low-volume groups. Based on this categorization, the association between hospital surgical case volume and the patient outcome measures was tested. Hospital patient case volume has significant effects on the total length of hospital stay for both THA and TKA and on the total cost for THA. Implications of the findings for practice are considered.