Paraneoplastic neurologic syndrome, a rare complication of carcinoma, includes various neurologic disorders, such as encephalomyelitis, paraneoplastic cerebellar degeneration, subacute sensory neuronopathy, retinal paraneoplastic syndrome, opsoclonus-myoclonus syndrome and stiff-person syndrome. Several antibodies to malignant tumor cells and neurons are detected in sera and cerebrospinal fluids of patients with this syndrome, however, there is no direct evidence of antiYo or antiHu antibodies' causative roles in neuronal loss. Recent studies showed cytotoxic T-cell activities against peptides of an antigen protein recognized by antibodies in the peripheral blood of patients with paraneoplastic cerebellar degeneration and antiYo antibodies, as well as in patients with antiHu syndrome. Treatment of paraneoplastic neurologic syndrome with plasmapheresis, immunosuppresive drugs, or intravenous immunoglobulin therapy has been attempted. Here, we discuss previous reports and theoretical treatments based on recent etiological hypothesis of paraneoplastic cerebellar degeneration.