Eight cases of malignant tumors originating in close proximity to various metallic surgical implants which were used in the treatment of common canine and feline fractures are presented. There were 5 osteosarcomas, one fibrosarcoma and 2 undifferentiated sarcomas with the characterisitcs of malignant histiocytomas. All 8 occurred in the md shaft of the femur, humerus or radius, a most unusual location considering that almost all primary canine osteosarcomas have been found tramedullary pins, 2 with intramedullary Steinmann pins (one with cerclage wires) and one with an AO plate screws. Seven of the fractures treated had united and only one pseudoarthrosis was present where the cerclage wires were used. All implants used showed corrosion and had been in place for 6 months to 6 years prior to tumor discovery. None was infected.