In the roes and wild boars inhabited the Dniprovsko-Orilskij Nature Reserve we identified nematodes’ eggs and larvae of orders Strongylida (Dictyocaulus sp., Muellerius sp., Cystocaulus sp., Protostrongylus sp., Ostertagiella sp., Globocephalus sp., Oesophagostomum sp.) and Rhabditida (Strongyloides papillosus (Wedl), S. ransomi (Scwartz)). The seasonal features in number of the ungulates’ nematodes in the environment are ascertained. It was found that females of palisade worms living in the ungulates’ airways do not release larvae in the environment from October to spring. In autumn the Rhabditida density in the environment is higher than in summer, but inversely, the number of Strongylida of alimentary canal – lower.