An examination has been carried out of 46 patients (33 females, 13 males, a mean age 40) with Sneddon's syndrome characterized by cerebrovascular disturbances and marked livedo. A clinical spectrum of the syndrome included miscarriage and intrauterine death of the fetus (20 cases), peripheral vein thromboses (12 cases), coronary heart disease (18 cases), thrombocytopenia (8 cases), arterial hypertension (27 cases), headache (39 cases), epileptic seizures (5 cases). Similar manifestations are usually seen in antiphospholipid syndrome (AFLS). Antibodies to phospholipids, those to cardiolipin, lupus anticoagulant were detectable in 78, 50 and 61% of the cases, respectively. Clinical and immunological signs of AFLS in the absence of SLE-typical symptoms provided grounds for considering them primary AFLS. Similar clinical patterns in 36 patients with cardiolipin antibodies and/or lupus anticoagulant and 10 patients without the antibodies and anticoagulant suggest these cases to be AFLS too.