Summary:-Shellfish is a highly nutritive and delicious food, consumed by largepopulation in different countries in the world, however, they may be carrying many parasitic agents transmissible to man where shellfish eaten raw orinadequately cooked, so this study was conducted to clarify the role of shellfishin transmitting some parasites to man. For this purpose, the following pointswere investigated:-I. Occurrence of trematode metacercariae ID shellfish andexperimental infection of puppies to determine the adulttrematodes species.14. Occurrence of protozoa oocyst or cyst in shellfish andexperimental infection of rats and puppies with Cryptosporidiumand Giardia.Ill. Experimental infection of fresh water crayfish, Procambarusclarkii with Trichinella spiralis larvae encapsulated IDdiaphragmatic pillars of pigs.A total of 2181 shellfish samples (1151 fresh water crayfish, 534 whiteshrimps and 496 blue crabs) were collected from different localities andProvinces. The collected fresh water crayfish samples from different localities atSharkia Province from the period extending from April 2004 to February 2005;included 305 crayfish from Abo-ELAkhdar canals at Zagazig city, 276 from EL-Shibrawain canals at Hehia, 298 from EL-Faridia canals at Abokebeer and 272from EL-Azyzyia canals at Menia EL-Kamh. The collected white shrimp