Change in tension along the iliotibial tract by sectioning its superficial layer was analyzed using 5 fresh whole cadavers, and the role of the superficial layer was investigated. Tibial attachment of the iliotibial tract (Gerdy's tubercle) was detached and pulled gradually in a distal direction with respect to the femur. Tension along the iliotibial tract by the distal movement of Gerdy's tubercle (stretching the iliotibial tract) was measured first when the whole iliotibial tract was intact, and then when the superficial layer was sectioned at different levels. When the superficial layer was sectioned above the greater trochanter, no significant change in tension was observed from that observed when the whole iliotibial tract was intact. When the superficial layer was sectioned at the middle of the thigh, the tension at Gerdy's tubercle was significantly reduced. It was concluded that not only Kaplan's fibers, those attached to the distal end of the femur and Gerdy's tubercle, but also the superficial layer of the iliotibial tract had an important role in producing tension at Gerdy's tubercle.