There had been no reports of Trichophyton tonsurans infection in Korea yet. We have much chances to import the organism through international travels and exchanges. But we, Korean, have no experiences to observe T. tonsurans. Author tried mycological studies with T. tonsurans isolated in New Orleans, USA. The results are as follows : Gross findings of T. tonsurans showed that fine granular surface with light yellow hue or white color and groving in the central area on the front side and mahogany brown color on the reverse side. On the urease test, various reddish discoloration was noted. Microscopic findings showed that septated hyphae, macroconidia, chlamydoconidia and microcondia. Macroconidia were 3-5 septated, smooth-surfaced, and were found more frequently in the whitish colony. Microconidia were characteristic in their arrangement and shape ; round or oval shaped microconidia laterally to hyphae, some were match-head like terminal swelling. Hair perforation test showed positive results in 16 strains among 19 tested strains. All these findings are similar to T. rubrum and T. menatgrophytes, the most frequent isolates of dermatophytes in Korea. And we have to pay an attention to diffentiate carefully.