Epidemiologic studies suggest that most sexual transmission of genital herpes occurs when persons shed virus but lack lesions. This study assessed 79 men (63 with a history of genital herpes simplex virus [HSV] type 2 infection, 5 with a history of genital HSV-1 infection, and 11 with HSV-2 antibodies but no history of genital herpes) and obtained daily swabs for viral culture. HSV was isolated at least once from 60 (81%) HSV-2-seropositive men. The total viral shedding rate in HSV-2-seropositive men was 5%; the subclinical shedding rate was 2.2%. Of 11 HSV-2-seropositive men without a genital herpes history, 7 recognized typical recurrences and HSV was detected in 10. The shedding rate among men with genital HSV-2 was significantly higher than among men with genital HSV-1 infection (odds ratio, 4.4; 95% confidence interval, 1.2-15.3). The frequency of viral shedding in men with genital herpes appears comparable with that in women.