Participants will give a medical history, undergo a physical examination, including genital examination, and receive counseling on safer sex practices and how to recognize signs and symptoms of a possible first episode of genital herpes. Source partners will also be counseled on transmission of genital herpes, and susceptible partners will be interviewed about their sexual history and practices. The source partner will be randomly assigned to take either a 500-mg tablet of valaciclovir or placebo (a pill with no active ingredient) daily for 8 months. All participants will be given diary cards to complete for a month-the source partner will record any drug side effects and the susceptible partner will record any signs or symptoms of possible HSV infection.