The most important contribution to the understanding and management of paraneoplastic neurologic disorders (PND) is the discovery that many of these diseases are immune mediated. It is believed that cytotoxic T-cell responses and antibodies that target neuronal proteins usually expressed by the underlying tumor cause the neurologic symptoms. The detection of these antibodies has provided diagnostic tests that allow recognition of the disorder as paraneoplastic and direct the search of the tumor to selected organs. This article summarizes the authors' findings of limbic encephalitis and postulates that a similar approach can be used for syndromes involving other areas of the nervous system.