The idiopathic osteonecrosis of femoral head is one of the orthopaedic dilemma in regarding the treatment and various trials to preserve the femoral head were known to be effective in the early stage of the disease process. The conventional methods of core decompression and bone graft were not usually indicated in the progressed cases that disclose the subchondral fracture or collapse of the femoral head. Authors reviewed 15 cases of the free fibular strut grafts performed for the progressed idopathic osteonecrosis of femoral head since 1983 at the Department of Orthopaedic Surgery, Daegu Fatima Hospital with follow-up periods from 2 years and 2 months to 4 years and 6 months except for 2 cases who had secondary procedures because of progressive collapse of the femoral head after the bone grafting and the following results were obtained; 1. The cases were 14 males and a female aging from 28 years to 56 years and revealed crescent signs in 9 cases and early collapses in 6 cases on the pre-operative x-rays with involvement in the other sides in 10 cases. 2. The successful results in clinical and roentgenological evaluations were obtained in 8 cases(53%) and progressive collapse was prevented in 10 cases(67%). 3. The exact insertion of the graft up to the subchondral level through the necrotic bone was essential and no weight bearing for 1 year was neccessary for success. 4. The free fibular strut grafts were effective to prevent the progressive collapse in progressed idiopathic osteonecrosis of the femoral head.