Dermatophyte infections and onychomycosis are not usually serious in term of mortality; however, they may have significant clinical consequences such as secondary bacterial infections, chronicity, therapeutic difficulties and esthetic disfigurement in addition to serving as a reservoir of infection. Our aim was to determine the prevalence of onychomycosis and dermatophytosis in a selected high risk group, consisting of male boarding school residents. A total of 410 males inhabiting two houses were evaluated by two dermatologists. In cases of clinical suspicion, appropriate samples were taken for direct microscopy and culture. The results showed that the prevalences of tinea pedis (athlete's foot) and pure pedal onychomycosis were 51.5% (n:211) and 4.4% (n:18), respectively. Thirty cases of those with tinea pedis were complicated by toenail onychomycosis. Tinea cruris was present only in five cases with tinea pedis. Interestingly 71.1% of those with tinea pedis and 45.8% of those with onychomycosis, associated with or without tinea pedis were unaware of their diseases. The most common fungal isolate was Trichophyton rubrum (76.6%) followed by Epidermophyton floccosum (11.6%), T. interdigitale (10.55%). Approximately one third of the cultures from nail specimens yielded pure growths of nondermatophyte moulds or Candida albicans. In conclusion, we found unexpectedly high prevalences of occult athlete's foot and toenail onychomycosis among the male residents of student houses. Our results indicate that health-care workers of such common boarding-houses should be more aware of clinical and subclinical dermatophyte infections and onychomycosis, and have more active approaches to educational measures and management strategies to prevent further infections. To our knowledge, this is the first epidemiologic study on the prevalences of dermatophytosis and onychomycosis in boarding-houses from Turkey.