Bartonella henselae can cause cat scratch disease and bacillary angiomatosis, a multisystem disorder seen primarily in patients with the acquired immunodeficiency syndrome. Both of these diseases are associated with neurologic complications, particularly encephalopathy. B. henselae may also cause bacteremia and endocarditis, and has been associated with aseptic meningitis and with dementia in patients also infected with the human immunodeficiency virus. Recent advances in identification of this difficult-to-culture organism will lead to recognition of more neurologic complications.