Systemic autoimmune disorders affect multiple organ systems. Brain involvement commonly causes seizures, which may be the presenting symptom. Systemic lupus erythematosus, Sjorgren's syndrome, Wegener's granulomatosis, sarcoidsosis, celiac disease, Crohn's disease, Behcet's, and Hashimoto's encephalopathy are reviewed. Mechanisms underlying CNS pathology in systemic autoimmune disorders-and specifically factors predisposing these patients-are discussed, including vascular disease (e.g., prothrombotic state, anticardiolipin antibody, emboli, vasculitis), antineuronal antibodies, immune complexes, cytokines, metabolic disorders, infection, and therapy. Diagnostic and therapeutic strategies must be individualized for both the disorder and the patient. Systemic autoimmune disorders affect multiple organ systems and frequently involve the central and peripheral nervous systems. Seizures are among the most common neurological manifestation and occasionally can be the presenting symptom. There are many causes of seizures in systemic autoimmune disorders (Table 1), and the first clinical challenge is to determine not only the cause but also the significance of seizures. In some cases, they are clues to metabolic or infectious disorders or medication toxicity; in other cases, seizures herald a life-threatening progression of the underlying illness.