We studied the conversion of T. rubrum from hyphae to spherical cells using the agar‐implantation method. Thirteen cultures of T. rubrum were isolated from tinea superficialis and granuloma trichophyticum and they were implanted into the peritoneal cavities of ddY male mice. The cultures were divided into three groups according to their parasitic forms. The first group consisting of two cultures were isolated from tinea unguium and tinea pedis (hyperkeratotic type); they were destroyed in the peritoneal cavities of mice by the sixth week. The eight cultures in the second group were isolated from tinea cruris, tinea circinata and tinea pedis (vesicular type); they converted to spherical cells and survived for 16 weeks. The three cultures of the third group were isolated from granuloma trichophyticum; they survived and grew as hyphal forms in the peritoneal cavities of mice for over 26 weeks without spherical cell conversion. In conclusion, the parasitic forms of the three cultures isolated from granuloma trichophyticum differed from the cultures isolated from tinea superficialis.

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