Despite the widespread success of total hip arthroplasties for treatment of arthritis of the hip, the procedure continues to be targeted for cost control. Our objective was to compare the total in-hospital cost of primary total hip arthroplasties in high-volume and low-volume hospitals. Data concerning the patient-level in-hospital costs of 940 consecutive primary total hip arthroplasties were extracted from the cost accounting system of three Canadian hospitals. Mean in-hospital costs for patients having total hip arthroplasties in a high-volume institution (> or = 300 total hip arthroplasties/year) compared with two low-volume Canadian institutions (< 300 total hip arthroplasties/year) were: overhead costs 1380 US dollars +/- 35 US dollars versus 2432 US dollars +/- 49 US dollars; direct costs 3023 US dollars +/- 93 US dollars versus 4952 US dollars +/- 91 US dollars and total costs 4403 US dollars +/- 117 US dollars versus 7385 US dollars +/- 1 US dollar 38, respectively (all comparisons in US dollars). Lower overhead and direct and total costs were found for primary total hip arthroplasties done in a high-volume Canadian hospital compared with the low-volume centers. Differences in direct costs, made up in large part by the implant cost, accounted for most of the disparity. As total hip arthroplasties continue to be scrutinized for cost containment, doing the procedure in a high-volume center seems to be an effective method of controlling costs.