A case of a 76-year-old man presenting with weakness of the lower legs and bilateral steppage gait is described. Neurological examination revealed a sensorimotor neuropathy with axonopathy and myelinic aspects. At the time of the diagnostic workup an episode of rectal bleeding occurred. Colonoscopy demonstrated an exophytic cancer of the sigmoid colon at 40 cm from the anal verge. At surgery the tumor adhered to the ileum, so a left hemicolectomy and ileo-ileal resection were performed. Tumor stage was Dukes' B, Jass III, Astler-Coller B2, T3N0M0. The patient underwent postoperative chemotherapy and was followed for the past three years. At present he is free of disease and the neuropathy has completely regressed without any dedicated therapy. As reported in the literature the appearance of a paraneoplastic neurological syndrome (PNS) may be the first sign of a malignancy that is occult at the time of clinical presentation. The most widely supported theory about its etiology is that of an autoimmune origin. The paraneoplastic neurological syndrome is considered to be at a point of intersection between tumor immunology, autoimmune neurological disease, and basic neurobiology. Previous experience has resulted in a pathogenic model and in a definition of a group of autoantibodies related to the disease. Small cell lung cancer (SCLC) is the neoplasm most frequently associated with PNS; other malignancies include lymphomas and various hematological malignancies. Some authors reported also that the percentage of patients with a high titer of neuronal autoantibodies is small and several of the autoantibodies are present at low levels without any accompanying clinical manifestation. In a clinical retrospective study of the Mayo Clinic Group 115,081 patients were examined over the period 1984-1993 and only 58 patients (0.05%) could be defined as being affected by a paraneoplastic neurological syndrome. Only five of these patients had colon tumors. The number of patients is so small and so widely scattered among publications that no statistical analysis is possible. Probably the only possibility for early identification of such a syndrome is a high degree of suspicion. In fact, these patients are usually first admitted and studied in a neurological unit, and the diagnosis of a tumor-associated disease is a delayed event.