During clinical and electromyographical examination of one patient with diabetic and one with alcoholic polyneuropathy we found an especially severe lesion of the ulnar nerve at the elbow on one side. As the polyneuropathy generally affects the nerves symmetrically we presumed in addition some other most probably ulnar nerve compression syndrome at the elbow. Both patients were operated and the nerves were transposed (Prof. NIGST). The local finding during the operation, the improvement of the paresis of ulnar nerve and the worsening of the polyneuropathy--found simultaneously at control after 2 and 4 years--confirmed our supposition. Should in cases of polyneuropathy an especially severely damaged nerve be found, one ought to think of the possibility of an additional mechanical lesion and treat the patient accordingly.