In order to increase the positive rate of cultre for dermatophyte infections of the nails, the authors devised the new file method. It is to perform the KOH mount arid culture with fine subungual hyperkeratotic debris obtained from the hyponycLium after grinding the nail plate from the surface to the bottom using various files, And we compared the result of this new method with that of conventional scraping and punch methods in 40 toenails and ]1 fingernails. The positive rate of culture for tinea unguium by three different methods was as follows: It was 52.5%(21 cases) through conventional scraping method, 70% (28 cases) through punch method and 80% (32 cases) through file method in the 40 toenai ls. lt was 18.2% (2 cases) through punch method, 27. 3% (3 sases) through scraping method and 54. 6%(6 cases) through file method in the 11'fingernails. In conclusion, the file method was found to be a more effective and successful method to detect the causative organisms of tinea unguium and was also easy to handle.