Infiltrative polyneuropathy is an infrequent complication of lymphoma or leukemia. The polyneuropathy can occur in patients with known malignancy, but sometimes it has been initial manifestation of underlying disease. The diagnosis was usually made at autopsy, because more common causes of polyneuropathy were frequently considered during life and many cases showed negative results on sural nerve biopsy. We experienced a case of steroid responsive polyneuropathy due to infiltration of malignant T cell on peripheral nerves prior to lymph node biopsy.