EN
New and traditional techniques of electron microscopy, and successful attempts at an experimental infection of fish with cocidia provided a base for a considerable taxonomic revision within the group of the fish coccidia. The authors present contemporary views on the biology of these protozoans (life cycles, host specifity) and new systems of taxonomic classification according to Dykova and Lom (1983), Levine (1983) and, the most recent, according to Overstreet et al. (1984). The list of the fish coccidia described from Poland, in agreement with the system of Overstreet, is also presented.