Background : Thermotherapy was been shown to be effective in the treatment of some fungal infections. Dermatophyte are well grown at 25C rather than 37C or high temperature. Objective : An vitro test was done to assess the complemental effect and optimal conditions of local heating on the susceptability of T. rubrum to systemic antifun al agents. Methods : Microdilution susceptability test to ketoconazole and iraonazole was done using 96 well microplate. Eight strains of T. rubrum were isolated from patient, with tinea pedis and were cultured at 25C, 37C, and 42C for 1, 8 or 24 hours per day. VIII were checked at 4th, 7th, 9th day after inoculution. Results : The growth without antifungal agents at 37C and 42C were decreased by 80% and 50% of the growth at 25C respectively. Seven day after inoculation was the proper time to check the MIC. MIC50 of ketoconazole was the lawest at 42C for 24hours per day in value of 0.006ug/ml and 0.09pg/ml at 37C for 24hours per day, 0.37ug/ml at 42C from 8hours per day and 37C for 8hours per day. MIC at 42C for 1hours per day, 37C for 11 hours per day and 25C for 24hours per day were the san in value of 0.74 pg/ml. MIC50 of itraconazole was the lowest at 42C for 24hours per in value of 0.006pg/ml, 0.01 pg/ml at 37C for 24hours per day, 0.02ug/ml at 37C for 8 hours per day. MC at 42C for 8hours per day, 42C for 1hurs per day, 37C for 1hours and 35C for 24hours per day MIC were the same in value of 0.05 pg/ml. Conclusion : Incubation at 37C for 24 hours per day or 42C or 24 hours per day increased the susceptability of T. rubrurn to ketoconazole and itraconazole. (Kor J Dermatol 1995;33(2): 210-247)