The most frequent neurological complications of antiphospholipid antibodies syndrome (APS) are cerebral infarctions. In cases with recurrent strokes this syndrome may be associated with multi infarct dementia. We report the case of a 40-year old man presenting as "primary" APS with multiple cerebral infarctions. This patient had insidiously and progressively developed a cognitive impairment predominant in memory. The progressive encephalopathy associated with APS is very different from multi infarct dementia and could be caused either by a vascular mechanism (vascular occlusion with fibrin thrombi or disseminated vasculitis) or by an immunological mechanism.