AIDS: People with HIV are also frequently co-infected with herpes simplex viruses (HSV), although the interactions between the two are not fully understood. Evidence suggests that HSV is a risk factor for the transmission of HIV, is a common opportunistic pathogen in HIV-infected persons, and that HSV reactivation appears to regulate HIV replication. The clinical significance of these interactions is not well defined. Current information about the HSV-HIV interaction is reviewed, and future research projects are suggested. Advanced HIV infection has been associated with genital herpes, and unusually severe outbreaks of genital herpes and persistent herpetic ulcerations are an AIDS-defining diagnosis. Chronic anti-HSV therapy may be beneficial in some persons with HIV. Studies are being designed to address some of the outstanding issues in understanding the links between the two infections, and potential volunteers in the trials are invited to participate. Contact the University of Washington Virology Research Clinic for further information.