The antifungal activity of ether extract of Nigella sativa seed and its active principle thymoquinone was tested against eight species of dermatophytes: four species of Trichophyton rubrum and one each of Trichophyton interdigitale, Trichophyton mentagrophytes, Epidermophyton floccosum and Microsporum canis. Agar diffusion method with serial dilutions of ether extract of Nigella sativa, thymoquinone and griseofulvin was employed. The incubation was carried out at 30 degrees C for 14 days. The diameter of fungal colonies and the percentage inhibition of the fungal growth at each dilution were determined, taking those of the controls as 100%. The minimum inhibitory concentration (MIC) was considered as the minimum concentration of the drug, which inhibited 80-100% of the fungal growth. The MICs of the ether extract of Nigella sativa and thymoquinone were between 10 and 40 and 0.125 and 0.25 mg/ml, respectively, while those of griseofulvin ranged from 0.00095 to 0.0155 mg/ml. These results denote the potentiality of Nigella sativa as a source for antidermatophyte drugs and support its use in folk medicine for the treatment of fungal skin infections.