The most characteristic types of microscopic vascular lesions in patients with various inflammatory systemic connective tissue diseases are described on the basis of the literature as well as biopsy and autopsy studies of the Pathoanatomy Department of the Institute of Rheumatology. Special emphasis is laid on diseases in which the nervous system involvement is not infrequent. Irrespective of the character of the observed vascular lesions, they result in occlusion of the lumen or a vessel wall rupture. In both the peripheral and central nervous system involvement these vascular lesions are accompanied by a variety of neurological manifestations. In rheumatoid arthritis necrotizing arteritis and intimal proliferation may result in neurological symptoms mostly peripheral, while CNS disorders are extremely rare. In polyarteritis nodosa in as many as over 50% of patients symptoms of peripheral or CNS involvement are observed. Their ischemic or hemorrhagic lesions result from occlusive arteritis nacroticans or from a rupture of altered vessel walls, respectively. In systemic lupus erythematosus CNS involvement (noted in 25-75% of patients) is due to dispersed thrombotic or inflammatory vascular lesions associated with immune complexes deposition or circulating antiphospholipid antibodies. The latter are probably related to the emergence of thrombosis or intimal proliferation of vessels.