A total of 300 fishes examined related to 10 marine fish species, out of which 193 samples proved to harbour Ichthyophonus hoferi (64.3%) from Lake El-Temsah and Suez Canal. The percentage of isolation was higher in winter (74%) than in summer (51.6%). The results of dinical investigation revealed that, some naturally infected fishes did not show any clinical abnormalities, while, other suffered from emaciation, exophthalmia, abdominal swelling and erection, easily detached scales. P.M. lesions were manifested as white nodules of Ichthyophonus hoferi in liver, kidney, heart, spleen and intestine. Ichthyophonus hoferi was isolated in Sabouraud's dextrose agar plate +1% calf serum and in Minimum Essential Medium + 10% fetal calf serum at pH 3, 5, 7 and 9 within 10-15 days. Morbidity and mortality rates, dinical signs and post-mortem changes in experimentally infected fish were discussed in details with reference to mycological significance of the causative agents.