Injuries to the peroneal or tobial divisions of the sciatic nerve occur in approximately 0.7-7.6% of patients undergoing total hip arthroplasty. No prior studies have investigated the incidence of injury to the superior or inferior gluteal nerves during hip surgery. This study evaluates the incidence of injury to the superior and inferior gluteal nerves in 55 patients undergoing total hip arthroplasty using a newly devised EMG scoring system. Subclinical gluteal nerve injury was documented in over 77% of patients, whether a posterior or a lateral approach to the hip was used.