As many as 30 patients suffering from systemic lupus erythematosus (SLE) with the clinical signs of central nervous system derangement were examined. The mean age of the patients was 31.1 years. Using EIA, antibodies against cardiolipin (a-CL) were detected in 21 patients (70%). A-CL were revealed in all the patients with cerebral circulation impairment (CCI), choreic hyperkinesis, and convulsive syndrome. A-CL were discovered in 12 out of 18 SLE patients suffering from migraine-like headaches and in 4 out of 5 patients with mental disorders. Antibodies reacting with cardiolipin were mostly represented by the IgM isotype (80%) whereas a-CL-IgG were only identified in 13% of the patients, being associated in all the cases with a-CL-IgM. The high level of a-CL-IgG in blood serum was recorded in patients with the gravest patterns of nervous system derangement: CCI, occlusion of the retinal artery, psycho-organic and convulsive syndromes. All these patients demonstrated generalized reticular livedo. The high levels of a-CL-IgM were observed in SLE patients with choreic hyperkinesis and migraine-like headaches. Thus, the studies made it possible to trace the relationship between the development of certain neurological disorders (CCI, chorea, convulsive syndrome) in SLE patients and a-CL.