Genital herpes simplex virus infections. There has been a dramatic increase in patient visits to physicians for evaluation and treatment of genital herpes infections. This has resulted in part from an increase in genital herpes infections, particularly severe, first-episode genital herpes infections in adults without prior HSV-1 infection. Virus culture remains the most sensitive and specific method for diagnosis, and use of viral cultures is encouraged. Type-specific antibody tests have been employed in studies documenting the role of asymptomatic shedding of HSV in transmission of genital infections, the role of genital HSV in transmission of HIV, the predominance of asymptomatic and unrecognized infections in those infected with HSV-2, and the presence of past asymptomatic or unrecognized acquisition of HSV-2 in 25% of persons presenting with first-episode genital herpes. Unfortunately, commercially available serologic tests do not reliably differentiate between antibody to HSV-1 and HSV-2. Recent studies suggest that the annual risk of transmission from a sexual partner with genital herpes is about 10% in heterosexual couples. Currently, promotion of "safe sex" is the only available approach for prevention of transmission. However, ongoing research is focused on the development of an effective vaccine. Acyclovir should be used routinely in persons with first-episode genital herpes, but careful evaluation is needed in persons with recurrent genital herpes to determine whether episodic or suppressive treatment is indicated. Acyclovir should also be used routinely for episodic or suppressive treatment of HSV infections in persons with AIDS. Additional antiviral agents are needed for more effective suppressive therapy and for treatment of ACV-resistant HSV infections in the immunocompromised host. 