It is well known that peripheral neuropathy occurs in patients with myeloma or macroglobulinaemia, but its pathogenesis is still obscure. In recent years, neuropathy has also been reported in association with benign monoclonal or oligoclonal gammopathy. Modern histo-immunological methods have revealed evidence of antibody production to peripheral nerve tissue, probably the myelin sheath. The present study included 21 unselected, consecutive patients with benign monoclonal gammopathy observed in the Division of Haematology. Clinical and laboratory investigations included electrophysiological examination and analyses of the M components. Of the 21 patients 11 had noticed slight neuropathic symptoms in their extremities; in 5 both clinical and electrophysiological findings were compatible with neuropathy; 6 showed positive clinical signs of neuropathy; 4 had either positive electromyographic or electroneurographic findings. In summary, 15 of 21 patients had some signs of peripheral neuropathy. In spite of the screening design of the study, this strikingly high frequency is comparable with other recent reports. Haematological studies did not reveal any significant differences between the patient groups with positive or negative neurological findings. The findings indicate that even benign gammopathies may be associated with peripheral neuropathy.