The purpose was to analyse two reported risk factors on the outcome of Birmingham hip resurfacing (BHR). We reviewed consecutive BHR arthroplasties and found 1,476 cases eligible for analysis. The mean follow-up was 7.3 years. Patients were classified into groups according to their head size and body mass index (BMI). Statistical analysis examined the follow-up Oxford Hip Scores (OHS) and revision rates between groups. In the large head group (50mm and above) the OHS was 0.5 points higher (p=0.003) than the small head group. In the non-obese group (BMI <30) it was 0.3 points higher (p=0.007). No significant difference in the survival of the implants by either head size or by BMI was detected. BHR is a suitable option offering good survival and higher functional outcomes in non-obese patients (BMI<30) with larger femoral head diameters (50 and above). Although results are statistically significant such a small difference in OHS will rarely show significant clinical difference. Therefore, despite.