In the evaluation of anthelmintic efficacy by fecal egg counts for cattle naturally infected with helminths, the reasonable technique of fecal egg counts and the reliable guidelines were determined. Modified technique of Harashigeru and Kim's sedimental tube was the most reasonable in fluke egg counts. Universal egg counting technique was preciser than McMaster egg counting technique and was lower in coefficient variation. Fecal egg counts of pretreatment should be carried out twice and mean of the egg should be calculated

General characteristic of parasitologic situation at the exclusion zone, some aspects of new conditions influence on separate systematic groups of mammal parasites Polesye State Radiation and Nature Reserve of the Republic of Belarus were presented. Research of helminth fauna and helminthological situation was realized by an example of 1 European bison, 7 mooses, 20 roe deers, 26 boars, 25 wolves, 50 racoon dogs, 6 foxes and 3 beavers. Scatoscopy of the animal excrements was realized by Kalantaryan method with saturated solution of sodium saltpeter, Berman method. Research results revealed 66 helminth species belonging to 4 classes and 34 families. There were found 10 parasite species at bison, 16 – at mosses, 17 – at roe deers, 16 – at boars, 8 – at deers, 23 – at wolves, 13 – at raccoon dogs, 13 – at foxes, 9 – at badgers and 1 – at beavers. Analyze of helminthofauna of the analyzed area showed that the nature reserve had its own helminthes complex. A lot of stated helminth species were parasites with a wide range of hosts, including domestic animals, and cattle. Wolves, foxes and raccoon dogs were hosts of some custodies invasions. Carnivorous animals and murine rodents were hosts of trichinosis invasion, which was stated at 41,2 % of raccoon dogs, 33,3 % of foxes and 16,7 % of wolves. Also trichinas were stated at bank vole (1,3%), yellow-necked mouse (2,7%), and house mouse (16,6%)