Two strains of the dermatophyte Epidermophyton floccosum were treated with seven new synthetic azole derivatives to determine their possible antifungal activity. Among these, two diazopyrazoles (1-phenyl-3-methyl-4-diazo-5-methanesulphonamid and 1,3-dimethyl-4-diazo-5-methanesulphonamid) and the triazole (4-methyl-6-t-butylpyrazolo[3,4-d][1,2,3]triazole) were inactive at the highest dose tested (100 μg/ml). The 4-methyl-6-phenyl-pyrazolo[3,4-d][1,2,3]triazole produced only a partial inhibition of growth, whereas the most active compounds were the two thiadiazines(6H-3-phenyl-5-methyl-7-(3,4-dichlorophenyl)pyrazolo[3,4-c] [1,2,5]thiadiazine-2,2-dioxide and 7-methyl-2-phenyl-4H-pyrazolo[1,5-c][1,3,5]thiadiazine-4-one), and an aminoisoxazole (3-methyl-5-aminoisoxazole-4-thiocyanate), which induced a remarkable and sometimes complete reduction in the growth rate of the fungus. The structure-activity relationships are discussed.