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.soya beans, 27 hay, 13samples of poultry ration 10 samples of eachbroiler concentrates, meat and bone meal, and layer concentrates)were subjected to mycological examination. The isolated fungi fromsingle feed samples represented ten genera. The most predominantgenus in all types of single feed was Aspergillus species which wasisolated from all samples. whereas, other genera were isolated invariable orders in the different single feeds. For instance, isolationfrequency was in yellow corn samples, Aspergillus spp. was isolatedfrom all samples (100%), followed by Rhizopus spp. (95%), Mucorspp. (45%) and Penicillium spp. (30%). In hay samples thepredominant isolates were Aspergillus spp., followed by Penicilliumspp., Cladosporium spp., Fusarium spp. and Alternaria spp. (93%,93%, 70%, 65% and 49 %) respectively.In soya bean samples the predominant isolates were Aspergillusspp., followed by Penicillium spp., Mucor spp. Rhizopus sppCladosporium spp., Scopulariopsis spp. and Alternaria spp. (100%,75%, 24%, 23%, 18% and 17%) respectively. in wheat samples themain genera fungus isolated were Aspergillus spp. (96%), followed byPenicillium spp. (85%), Rhizopus spp. (450/0), Mucor spp. (27 0/0)