The authors investigated the effect of a posterior surgical approach on the local femoral blood supply during primary total hip arthroplasty. Greater trochanteric blood flow measurements were made with a laser Doppler flowmeter at intervals during the performance of eight uncemented and nine cemented total hip arthroplasties. Complete detachment of the quadratus femoris was associated with a significant decrease in trochanteric blood flow in the uncemented and cemented groups. The lowest perfusion levels during the procedure were seen transiently with posterior dislocation of the femoral head, after which trochanteric perfusion was decreased by 66% in the uncemented group, and 61% in the cemented group compared with baseline values. Blood flow remained approximately half of baseline values after insertion of the femoral prosthesis in the uncemented and cemented groups. These changes in greater trochanteric blood flow may serve as a marker for reduction in proximal femoral blood flow during total hip arthroplasty, and subsequently relate to the extent of bony ingrowth, periprosthetic bone loss, and ultimately the incidence of implant failure caused by aseptic loosening.