OBJECTIVES: Total Hip Replacement (THR) is regarded as gold standard treatment for degenerative hip disease in elderly patients. Young, active patients, however, are a more challenging group for THR due to the high risk of revision and associated complications. In 2002, the National Institute for Health and Clinical Excellence (NICE) recommended MoM hip resurfacing as a treatment option for this patient group. An alternative treatment for these patients is watchful waiting (WW) whereby patients are maintained on drug-based regimens until they are old enough to warrant a THR. The aim of this study was to evaluate the cost-effectiveness of BHR vs. WW in 45 – 55 year old patients with severe hip damage. For completeness the cost-effectiveness of BHR vs. THR was assessed in the same patient group. METHODS: A health economic model was constructed to assess the efficacy, cost and health-related quality of life associated with BHR, WW and THR treatments. Efficacy data for BHR were obtained from a large, prospective database (n=4,424), which provided up to 5 years follow-up for individual BHR patients. Resource use and utility data were obtained from published sources. The primary outcome from the model was the cost per quality-adjusted life-year (QALY). RESULTS: Preliminary results demonstrate that at year 5 BHR has an incremental cost/QALY (ICER) of £1,101 compared to WW and an ICER of £13,125 compared to THR. Over time the ICER decreases and BHR becomes dominant (i.e. it is more effective and costs less) compared to WW and THR by year 20 and 15, respectively. CONCLUSIONS: This study demonstrates that in patients aged 45 - 55 years with severe hip damage, BHR offers an extremely cost-effective alternative to WW with an equivalent improvement in quality of life to THR. Patients treated with BHR will benefit from significant health gains at an acceptable cost.