In vitro sensitivity of T. mentagrophytes against antifungal agents was investigated. The 20 strains of T. mentagrophytes were tested. They were 5 strains of granilar form, 5 of powdery form, 5 of persicolor form, and 5 of downy for m. The tested antifungal agents were griseofulvin, ket,oconazole and it,raconazole. The results were as follows : 1. Minimal inhibitory concintration(MIC) of antifungal agents against, T. mentagrophytes : MIC of griseofulvin was 3.13-25 ug/ml, the highest level, that of ketoconazole was 0.05-12 ug/ml, and that of itraconazole was 0.025 6.25 ug/ml, the lowest one. 2. MIC of antifungal agents against T. mentagrophytes strains. MlC of griseofulvin was 12-25 ug/ml on granular form and 3.13-25 ug/ml on the other forms. MIC of ketoconazole was 0.39-12 ug/ml on granular form, 0,05 0.78 ug/ml on powdery form, 0.05 12 ug/ml on persicolor form, and 0.1-12 ug/ml on downy form. MIC of itraconazole was 0.39-6.25 ug/ml on granular form, 0.05-0.39 ug/ml on powdevy form, 0.025-0.05 ug/ml on persicolor form, and 0.05-0.1 ug/ml on downy form. Granular form showed the highest level of MIC among antifungal agents. These findings suggesed that, itraconazole was the most arctive drug against T. mentagrophytes and the pranular form showed the lowest, sensirivity against antifungal agents. (Kor J Dermatol 1992;30(6):769-775)