The financial and medical records of 98 patients undergoing either primary total hip or total knee arthroplasty were analyzed to determine the inpatient cost of their surgery. Eleven patients were excluded, leaving a total of 87 patients available for analysis who underwent 50 primary total hip and 37 primary total knee arthroplasties. Ten separate cost centers such as implant, anesthesia/operating room, nursing/hospital room, physical therapy, and laboratory were included in the evaluation. Correlations between total cost and demographic parameters such as patient sex, age, and length of stay were determined. Seventy-six percent of the inpatient cost of all total joint procedures consisted of implant, anesthesia/operating room, and nursing/hospital room costs. Reductions in the cost of these components represent a potential for cost containment. The strongest correlate for total cost was hospital length of stay (P < .0005). Unfortunately, there is evidence that length of stay has reached a plateau and cannot be reduced further without affecting the quality of care and the incidence of complications.