Neurofibromatosis was recorded from 30 in 82,249 postmortem cases (0.036%) at the Medical Academy of Erfurt, Institute of Pathological Anatomy, between June 1, 1945 and December 31, 1986, among them 13 cases of classical peripheral neurofibromatosis generalisata Recklinghausen (NgR) and 17 with CNS involvement. These had been 10 males and 7 females who had died at an age from 8 to 77 years (average age and death being 39 years). CNS lesions were preferentially localised in periventricular sections of the third and fourth ventricles and the cerebral aquaeduct, with diffuse gliosis being recorded from 5 cases. Typical bilateral neurofibromatosis of the acoustic nerve was established from three males aged 19, 26 and 30 years. Spinal neurinoma or neurofibroma, meningioma, an astrocytoma of the cervical spinal cord, and leptomeningeal sarcomatosis were also recorded. Additional skeletal abnormalities were exhibited by four cases. Interest is generally growing in CNS involvement in neurofibromatosis due to the possibility of intravital diagnosis by computed tomography (CT) and magnetic resonance spectroscopy (MRI) and because of possible surgical therapy. Recent studies in molecular genetics, on the other hand, have shown classical NgR to be caused by a lesion to chromosome 17, while bilateral neurofibromatosis of the acoustic nerve was found to be based on a genetic defect to the long arm of chromosome 22.