Clinicopathological findings of three different neoplastic conditions involving the spinal cord and nerve roots in three dogs are described. One sarcomatous intramedullary tumor closely associated with the vasculature was classified as a reticulum cell sarcoma of the spinal cord. The second case had massive and widespread neoplastic proliferation of reticulohistiocytic cells around the perineurinal vessels of many spinal nerve roots. The process was classified as a primary neoplastic reticulosis of the spinal roots. Multiple highly malignant tumors, infiltrating the spinal cord were found in one thoracic and several lumbosacral spinal nerve roots in the third case. These were considered to be anaplastic neurofibrosarcomas because of high collagen content, intact nerve fibers, whorl formation, and the tendency to palisade in some areas.