We report a case in which a patient having curettage and resection of a presumed benign lesion of the tibia (later recognized as osteosarcoma) had probable iatrogenic transplantation of tumor to the contralateral iliac crest, which had served as a donor site for bone chips used to pack the tibial lesion. The patient later had above-knee amputation for the primary tumor and eventually required contralateral hemipelvectomy when tumor developed in the iliac crest donor site. We discuss the literature of tumor transplantation and seeding in operative settings and stress the clinical importance of avoiding possible tumor contamination of operative fields by meticulous instrument changes and by isolation of multiple surgical fields.