Fifty specimens Clarias lazera fish were collected from different fish markets in Assiut city and examined grossly and microscopically for the presence of trematode encysted metacercariae in their muscles. The incidence of infestation was found very high (92%). Two forms of encysted metacercariae were detected, one form appeared grossly as whitish raised nodules, while the other form appeared only by microscopic examination. They were those of Cynodiplostomum azimi and Prohemistomum vivax respectively. Histopathological examination of fish muscles of Clarias lazera showed degenerative, necrotic and inflammatory changes. Parasitic granuloma were detected among degenerated muscle fibers. Fibrosis and calcification were observed as a response of tissue against the parasite.