The incidence of mycoses is high in Madras accounting for over 13% of dermatoses diagnosed in a three-year period. Dermatophytoses (tinea corporis and tinea cruris) and pityriasis versicolor were most common in May and October. A correlation was observed between these infections and environmental temperature, humidity and rainfall. Most cases of all dermatophytoses except tinea capitis were recorded between 10 and 30 years of age but the latter was most common between one and 10 years. Males were predominantly affected with all except tinea axillaris, candidiasis and piedra. The incidence of piedra and deep mycoses was low.