Background and Methods. Herpes simplex virus type 1 (HSV-1) has been identified as a cause of cutaneous or ocular infection among athletes involved in contact sports; in this context it is known as herpes gladia-torum. In July 1989, we investigated an outbreak among 175 high-school wrestlers attending a four-week intensive-training camp. Cases of infection were identified by review of medical records, interview and examination of the wrestlers, and culture of skin lesions. Oropharyngeal swabs were obtained for HSV-1 culture, and serum samples for HSV-1 serologic studies. Results. HSV-1 isolates were compared by restriction-endonuclease analysis. HSV-1 infection was diagnosed in 60 wrestlers (34 percent). The lesions were on the head in 73 percent of the wrestlers, the extremities in 42 percent, and the trunk in 28 percent. HSV-1 was isolated from 21 wrestlers (35 percent), and in 39 (65 percent) infection was identified by clinical criteria. Five had conjunctivitis or blepharitis; none had keratitis. Constitutional symptoms were common, including fever (25 percent), chills (27 percent), sore throat (40 percent), and headache (22 percent). The attack rate varied significantly among the three practice groups, ranging from 25 percent for practice group 1 (lightweights) to 67 percent for group 3 (heavyweights). Restriction-endonuclease analysis identified four strains of HSV-1 among the 21 isolates. All 10 isolates from practice group 3 were identical (strain A), and 5 of 7 isolates from practice group 2 (middleweights) were identical (strain B), which suggested concurrent transmission of different strains within different groups. HSV-1 was not isolated from any oropharyngeal swabs. Conclusions. Herpes gladiatorum may cause substantial morbidity among wrestlers, and it is primarily transmitted by direct skin-to-skin contact. Prompt identification and exclusion of wrestlers with skin lesions may reduce transmission. (N Engl J Med 1991; 325:906–10.).