Dermatophytes are keratinophilic fungi that infect keratinized tissues causing diseases known as dermatophytoses. Dermatophytes are classified in three genera, Epidermophyton, Microsporum, and Trichophyton. This investigation was performed to study the prevalence of dermatomycosis among 640 patients being evaluated at the dermatology clinics at Kasr elainy, El-Husein and Said Galal hospitals in Cairo and Giza between January 2005 and December 2006. The patients were checked for various diseases. Tinea capitis was the most common clinical disease followed by tinea pedis and tinea corporis. Tinea cruris and tinea unguium were the least in occurrence. Tinea versicolor also was detected. The most susceptible persons were children below 10 years followed by those aged 31-40 years. Unicellular yeast was the most common etiological agent and T. tonsuranswas the second most frequent causative agent followed by M. canis.