Over a one-year period the cerebrospinal fluid (CSF) obtained from a series of homosexual men immunocompromised with either Hodgkin's disease or acquired immune deficiency syndrome (AIDS) was cultured to assess the frequency with which infectious viruses could be recovered. Of 58 patients examined, 4 (6.9%) had CSF cultures that showed a cytopathology consistent with a virus infection. All isolates proved to be herpesviruses. Cytomegalovirus (CMV) and varicella-zoster virus were isolated from CSF obtained from 2 patients with neurological features consistent with a subacute encephalitis common among AIDS patients. CMV was also recovered from the CSF of an AIDS patient who developed an ascending myelitis of herpesvirus origin. Finally, a CSF sample obtained from an immunodeficient homosexual man who showed no detectable neurological abnormalities consistently yielded herpes simplex virus type 1 in culture. These results suggest that seeding of the CSF with infectious virus is an uncommon event in this patient population. However, our experience should not dissuade attempts to culture viruses from CSF in similar cases. Successful isolations may prove beneficial in the diagnosis of an accompanying neurological illness and facilitate treatment with antiviral therapy when indicated.