Among 234 haemophiliacs (A and B) treated between 1948 and 1975 at the First Medical Clinic of the University of Vienna, 25 (10.8%) with 36 peripheral nerve lesions have been observed. This amounts to 15.3% or 2.4 lesions within 100 observation years. The average age of the patients at the time of development of lesion was 26.4 years. Correlations between severity of haemophilia and frequency of occurrence of lesions were found. Patients with mild haemophilia did not show peripheral nerve disturbances. The numbers of times individual nerves were affected are as follows: maxillary (1), radial (2), medial (6), ulnar (4), obturator (1), lateral cutaneous nerve of thigh (1), femoral (12), including lesions of the 2nd and 3rd lumbar roots, sciatic (6), including lesions of te 5th lumbar and the 1st sacral roots, peroneal (3), and tibial (1). In 1978, 11 patients who previously had sustained 16 peripheral lesions were reexamined. Of these, 10 had fully recovered, 4 showed some persisting sensory disturbances, and 2 were unchanged. Motor nerve conduction velocity, distal latency and compound nerve action potentials were systematically examined in 11 cases on both sides of the body. In contrast to our expectations, no signs of subclinical peripheral nerve lesions were found. The comparability of the presence and previous results is discussed.