that up to one half or

Shortly after HIV was identified as the agent responsible for AIDS, it was learned that H I V could be isolated in the brains of demented, seropositive individuals (Ho et al., 1985) and that, in fact, H I V could even be found in the cerebrospinal fluid in half or more of asymptomatic, HIVseropositive persons (Resnick et al., 1985; Resnick et al., 1988).