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In this study, we tried to find out the morphological changes following the UVB-irradiation on these fungi and analyze the obtained results in molecular aspect. The following species of dermatophyte fungi (Trichophyton rubrum, Trichophyton mentagrophytes, Epidermophyton floccosum and Microsporum canis) have been isolated from patients and selected for investigation in this project. For determining the possible molecular changes in dermatophytes due to UVB-irradiation (e.g. apoptosis feature), we next isolated high molecular weight DNA from non-irradiated as well as irradiated T. rubrum and compared them by gel-electrophoresis. The result of study indicated the inhibition of growth in irradiated colonies. The longer irradiation time caused slower rates of growth in these fungi. Besides, the changes in shape of colonies and pigmentation were observed in some cases. The microscopic studies of irradiated colonies indicate deformation of hyphae and changes in size and shape of macroconidia in all species. Besides, changes in number of microconidia in some species were determined. In the investigation of isolated DNAs from T. rubrum no differences in DNA banding patterns (apoptosis) was observed