Biological activity of natural products on dermatophytes has been studies by testing some essential oil from medicinal plants against the growth of three dermatophytic strains, Trichophyton mentagrophytes, T. rubrum and Epidermophyton floccosum. From the results of disk diffusion technique indicated that pepper oil and basil oil could inhibit their growth quite well with minimum inhibitory concentration (MIC) of pepper oil 54.53, 109.05 and 69.80 mug/ml and of basil oil 34.50, 72.36 and 96.66 mug/ml on T. mentagrophytes, T. rubrum and E. floccosum, respectively. The GC/MS analysis of essential oils indicated that the main component of pepper oil was Limonene (73.95%) and Anethole (94.92%) was found to be the main component in basil oil. Interestingly, the main component obtained from pepper oil, Limonene, and of basil oil, Anethole, could perform the average size of inhibitory zone of 32.8, 21.0 and 41.2 mm., and 22.7, 20.0 and 14.3 mm. on the growth of T. mentagrophytes, T. mentagrophytes, T. rubrum and E. floccosum, consecutively.