Resurfacing THA is an attractive treatment option for young patients because it saves the femoral head and is easily revisable. We assessed the clinical outcome of metal-on-metal hybrid total hip resurfacing for the treatment of 295 patients (350 hips) younger than 50 years of age (average, 41.2 years) and compared these results with those of patients 50 years or older (average, 57.4 years) at the time of surgery who were implanted with the same design. Seventy-five percent of the patients were male. The minimum followup was 2 years (mean 5.5 years; range 2-9 years). UCLA hip scores improved to 9.4 for pain; 9.6 for walking; 9.5 for function; and 7.6 for activity. We found no differences in survivorship between younger and older patients, and postoperative clinical scores related to the patients' physical health were comparable. There was no acetabular component loosening. Ten hips (2.8%) were revised for femoral aseptic loosening and one for femoral neck fracture. The 5-year survivorship of hips with good bone quality was 97.8%. There has been no femoral component loosening when the femoral stems were cemented irrespective of bone quality. Metal-on-metal resurfacing THA performs well at short to mid-term followup in young, active adults despite high activity levels.