Summary:-The phaeoid (dematiaceous fungi) are a curious group of organisms capable of causing a wide array of clinical pathologies ranging from superficial to the deep seated infection.The present work was aimed to study the rate of dematiaceoous fungi in human and animal diseases as well as its occurrence in their environment. Five hundred nail scrapings samples from human onychomycosis, 90 animal samples including rectal swabs, claws While human specimens revealed 20 isolates (4%) of dematiaceous fungi, animal specimens gave 15 isolated (16.55%). On otherhand, examination of 90 environmental samples revealed the isolation of 13 isolates from the air (23.63%) and 6 isolates from soil (Out of 500 human nail scrapings specimens, 20 isolates of dematiaceous were obtained and identified into 4 genera as (7) Alternaria spp., (6) Cladosporium spp., (4) Hendersonula toruloidea, (2) Curvularia spp. and one of Phialophora species.from 90 animal samples, 15 dematiaceous isolates were obtained. They were identified into 7 genera namely Cladosporium, Alternaria, Rhinocladiella, Scytalidium, Nigrospora, Phialophora and Curvularia from cattle samples obtained Cladosporium spp. (3), Rhifrom horse samples obtained Alternaria spp. (4), Cladosporium spp. (2) and one isolate from each of Phialophora spp. and Curvularia spp. were identified.Concerning with environmental samples Cladosporium spp., (6) Alternaria spp. (5) and Curvularia spp. (2) were identified from air samples.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