A survey on myxosporean parasites of freshwater fishes from Mesopotamian part of Iran (south western part of the country, Khuzestan Province) was carried out. Some 280 individuals belonging to 14 different species were
examined during a period extending from 1994 to 1997. In this study we investigated the prevalence of myxosporean parasites, morphology of the spores,plasmodial development, the infective sites, and characteristics of the cyst location
using the histological approach. The collected parasites were as follows:
Myxobolus persicus, M. karuni, M. bulbocordis, M. nodulointestinalis, M. iranicus, M. mesopotamiae, M. shadgani, M. sharpeyi, M. molnari and M. mokayeri. Barbus sharpeyi and B. grypus, economically important fishes,
were infected by six and four myxosporean parasites respectivelly. All of the studied cases of infection were observed in the natural waters.