Thirty patients younger than 19 years with malignant bone tumors of the pelvis were treated by limb salvage surgery between 1970 and 1998. Functional and oncologic results were reviewed retrospectively. In 10 patients the defect was reconstructed by an endoprosthesis and in 20 patients reconstruction by autologous grafts (n = 7), allograft and prosthesis combinations (n = 2), bone cement reconstruction (n = 1), iliosacral arthrodesis (n = 1), modified Girdlestone procedure (n = 3), or resection without reconstruction (n = 6) was done. Three and one-half reoperations per patient were necessary postoperatively after allograft reconstruction, 2.5 reoperations per patient were necessary after endoprosthetic reconstruction, and 0.8 reoperations per patient were necessary after other or no reconstruction. After a mean followup of 52 months (range, 2-241 months), 17 patients were alive, 15 of whom were continuously disease-free, and 13 patients had died of their disease. Functional ratings were 81% after autograft, 73% after allograft, and 60% after endoprosthetic reconstruction. Defect reconstruction varied according to the type of resection. Type I resections were best reconstructed by biologic methods. Endoprosthetic reconstruction after periacetabular resection with the advantage of preservation of a functional hip and body integrity was associated with a high rate of complications and reoperations. Its role compared with allograft reconstruction, modified Girdlestone procedure, or no reconstruction requires additional investigation.