Outbreaks of Trichophyton tonsurans infection constitute one of the serious problems among combat sports practitioners in Japan. To facilitate the diagnosis of individuals at risk, we undertook a study to determine which body sites are most commonly infected. We reviewed medical data, hairbrush culture results and questionnaire information from patients with T. tonsurans infection who were admitted to the dermatology clinic of Juntendo University hospital from 2000 to 2004. The study included 92 patients (87 males), aged 6-38 years (mean age: 18.4 years old). Eighty-nine patients were judo practitioners and three were wrestlers. Twenty-eight patients (30.4%) were asymptomatic carriers. In 64 patients, 51 patients (55.4%) with tinea corporis, 27 patients (29.3%) with tinea capitis, and/or one patient (1.1%) with tinea manuum were seen. Tinea corporis was observed on the forehead, auricles, nape of the neck, bilateral shoulders, left side of the upper chest, both elbows, back of the left hand to the wrist and both knees. Tinea capitis was most common in the occipitonuchal region at the hairline and in the temporal and frontal regions, at both auricles. Initial screening of these sites might facilitate the identification of the infection especially in judo practitioners.