In Wegener's granulomatosis peripheral nerves are more often involved than central nervous structures; functional psychoses are secondary e.g. to renal complications. Neurologic-psychiatric symptoms are varied and result from local spread from the upper respiratory tract with separate granulomata and vasculitis. Striped muscle is involved in about 10% of cases. Specific vegetative disturbances of function do not appear to occur. This is also true for Granuloma gangrenescens. Its multicentric inflammatory, ulcerating and necrotic foci involve midline structures and often start at the anterior neuroporus. Becet's disease, however, shows clear characteristic localisation, symmetry of various dermatologic phenomena in the extremities and the almost obligatory involvement of mouth, stomach and the genitals and their surroundings. This one may assume to be due to a mesencephalic parasympathicotonic reaction as the basis for the occurrence of perioral and acro-syndroms after Fischer-Brügge and Sunder-plassmann. Some similarity with the localization of other collagenous diseases is evident. The anterior basal ganglia represent a favored focus where e.g. initial, imcomplete and readily recurrent processes, possibly of an exsudative nature, may start off neurovascular changes of limited areas without necessarily producing clinically detectable signs of the usual neurologic-psychiatric type. In Behcet's disease, rather as in scleroderma, the nervous system appears to be decisively involved. About one third of the cases show changes in the nervous system ("Neuro-Behcet" in the usual sense) with little peripheral signs and rare myositis. But Behcet's disease may also-like erythematodes or progressive sclerodermia-simulate a disseminated encephalomyelitis. The pathogenetic factors of Reiter's syndrome appear to be closely related. The relatively constant main symptoms are also localized and permit the conclusion that they depend on vasomotorically linked innervation of the first bulbar segment. The preference for distal localization of bilateral skin involvement hints - as in Behcet's disease at hypothalamic distribution; main localization in midface and the oral mucosa, in eyes and the ends of the midline and, often, also involvement of certain midline and, often, also involvement of certain favored joints permit the assumption of mutural relations between the cranial and sacral fields of incidence of the trophotrop-endophylactic system which is linked via the parasympathic with periphery. According to present knowledge the bundles of Schütz and, further, Krüke may be the pathways. Where pelvic processes predominate viscero-cutaneous or cuto-visceral reflexes may - as in dermatomyositis - be involved. E.g visceroreflectory changes explain coincidences of signs in similar or adjacent segments of the urogenital system, the rectum and certain joints. Psychose on a physical basis are rare. As in other collagen diseases the spinal cord is rarely involved, but "multiple sclerosis" may be simulated...