In 1991, a 67 year old patient, suffering from an adenocarcinoma of the colon, had to undergo hemicolectomy. In the five following years, isolated metastases developed in the liver and have been surgically removed. In 1997, acute mononeuritis multiplex appeared and nerve biopsy revealed vasculitis. There were no signs of inflammatory rheumatic illness, collagenosis, cryglobulinemia, infection or hypersensitivity to medication. We have therefore postulated a relation between the vasculitis and the malignancy. Tumorous relapse could however not be detected at that time. Under immunosuppressive therapy, the neurological deficiencies receded partially, though the carcinoma of the colon reappeared with systemic metastases in the wake of the vasculitis. Diagnostic measures and the relationship between malignancy and vasculitis are discussed.