This study was carried out on 800 cultured Nile catfish Clarias gariepinus. Fish were subjected to full clinical and laboratory examination of infectious parasitic and bacterial diseases & a diseases of unknown etiology called (Cracked head diseases), whi1-The isolation and prevalence of ectoparasitic and endoparasitic diseases from C. gariepinus could be identified as follow: The prevalence of helminthes parasites reached to 79% with the highest incidence of trematode (monognetic trematode 25% & dignetic trematodes 40%, cestodes (32%) and nematodes (33%). The prevalence was the highest in spring followed by summer, autumn and winter (86%, 82%, 78% and 70% respectively).While soil samples revealed Alternaria spp. (2), Stemphylium spp. (2) and one isolate from each of Phialophora spp. and Cladosporium spp.All dematiaceous isolates were identified by macromorphological and micromorphological characteristics after subculture on potato dextrose agar at 25ºC. Proteolytic activity of dematiaceous fungi on gelatin, tyrosin, casein medium were also used.As regard to antifungal sensitivity test in this work, the obtained data revealed that ketoconazole and itraconazole are the more effective drug upon tested dematiaceous fungi followed by amphotericin B and fluconazole while clotrimazole were less effecti