Infectious human immunodeficiency virus (HIV) was recovered from 30 of 48 cerebrospinal fluid specimens from seropositive persons with and without neurologic symptoms or disease. Of 16 patients with only neurologic problems or other HIV-related conditions, but not the acquired immunodeficiency syndrome (AIDS), 11 had virus recovered; over half of those with AIDS also had virus isolated. Patients with headache or altered mental status had the highest recovery rate of HIV from cerebrospinal fluid. Although virus was primarily found in patients with detectable neurologic disease, it was also isolated from 5 of 8 patients with normal neurologic examinations. Two of these patients had fever alone. The presence of virus in cerebrospinal fluid did not necessarily correlate with isolation of virus from the serum. These findings suggest that HIV may at times replicate preferentially in the brain and that its presence may not immediately cause neurologic signs or symptoms.