Rationale: Classic bacterial meningitis usually has a more acute and severe presentation than is described in this case. In patients with AIDS, Cryptococcus neoformans is the most common cause of meningitis. Tuberculosis is also an important consideration, because it is much more common in AIDS patients than in other populations. Other fungi are uncommon causes of meningitis. Brain abscess will often have associated focal neurologic findings. Syphilis is always a consideration, especially in AIDS, although it often manifests more indolently. Viral causes would not be expected to last this long. Other causes should always be considered, even though clinically, those possibilities are difficult to distinguish.