Eighteen cases of osteonecrosis of the femoral head associated with macromolecular polyvinylpyrrolidone (PVP) deposition were analysed on the basis of clinical, radiologic and pathologic features. The cases were observed during 8 years period from January, 1974 to December, 1981. The pathogenesis of the osteonecrosis of the femoral head due to PVP storage in reticuloendothelial system were discussed in detail. Parenteral administration of high-molecular PVP in repeated, long duration led to osteonecrosis of the femoral head. Storage of PVP in the histiocytes of the bone marrow resulted in osteonecrosis of the femoral head followed by microciculation disturbance. PVP-induced osteonecrosis were manifested as multiple foci of necrosis involving not only the femoral head, other long bones around joints, but also the visceral reticuloendo-thelial system characterized by infiltrates of histiocytes laden with PVP. The patients with PVP induced osteonecrosis complianed multiple joint pain in their early course of the disease. On roentgenogram, osteonecrosis were often noted in the hip, shoulder, knee, and ankle in order or frequency. Foamy histiocytes laden with PVP were characteristic on hematoxylin-eosin stain diagnostic on Weigert's elastica, phosphotungstic acid hematoxylin, and Congo red stains. As far as rationale of the treatment concerning a number of staging systems for Osteonecrosis, the choice of surgical procedures were similar to those given by W.F. Enneking et al. In the series, we have performed two hips in total surface replacement, 26 hips in total hip replacement mostly for 3rd generation-configuration of Charnley prosthesis. In addition, one case for free vascularized fibula graft and trans-trochanteric rotational osteotomy after Sugioka were also included for this study. The result of treatment was rather optimistic. However, complications have occured in 4 hips of 3 patients which required removal of whole prosthetic components. Therefore, we underwent revisional surgery in three out of four hips subsequently during the short post-poerative follow-up. These will be published in the future.