The mechanism for central nervous system (CNS) involvement in connective tissue diseases is variable. Although CNS vasculitis does occur in some connective tissue diseases, it is rare in many others, including systemic lupus erythematosus. Overall, the most common pathogenetic mechanism for CNS dysfunction in patients with connective tissue disease is probably secondary CNS involvement, due either to multiple systemic organ dysfunction (including hypercoagulable or hypofibrinolytic states) or due to CNS and systemic infections. The pathogenetic role of antineuronal antibodies is yet to be defined. Generally, nervous system complications of those collagen diseases that classically produce necrotizing vasculitis should be treated with cytotoxic agents. The less severe vasculitides, particularly temporal arteritis, respond well to steroids, as does sarcoidosis. There are a variety of mechanisms for nervous system disorders in complex multiple system diseases. The etiology is often outside of the nervous system, and results of therapy are highly variable.