During the examination of 182 owls--Asio otus (51), Strix aluco (44), Bubo bubo (34), Nyctea scandiaca (15), Athene noctua (14), Otus scops (9), Tyto alba (4), Aegolius funereus (3), Glaucidium passerinum (2), Asio flammeus (2), indigenous "owls" (4)--5 protozoan species, 3 trematode species, 1 cestode species, 6 nematode species, 3 acanthocephalan species, 2 acaride species and 7 insect species could be discovered. Dermanyssus hirundinis was proved on the Long-eared Owl and Carnus hemapterus on the Barn Owl for the first time. The infestation frequency of endo- and ectoparasites was from medium to intense on an average, whereas the infestation intensity was from small to medium. The highest rates of infestation were found at nematodes. A case of "pseudoparasitism" was detected and the significance of the analyses of stomach-contents as a guarantee of diagnosis was pointed out.