Four patients with recurrent stroke and multi-infarct dementia are presented in whom the dementia was progressive and severe. Three of the patients developed the dementia during the course of an illness which was punctuated by repeated episodes of cerebral infarction demonstrated by computed tomographic (CT) scans. The fourth patient presented with an illness dominated by progressive and deteriorating higher mental functions, which culminated in a major stroke 18 months later. Three patients fulfilled the American Rheumatism Association (ARA) criteria for the classification of systemic lupus erythematosus, the fourth had a 'lupus-like' disease. All had livedo reticularis, severe migraines, and also demonstrated antibodies to phospholipids. All four patients suffered deep vein thromboses.