The effects of the nematode Toxascaris leonina infection on the body weight and fur quality of the arctic fox have been experimentally studied. At infection dozes of 10 and 100 eggs of T. leonina per host no significant effect of host infection doze on the body weight and pelt quality of arctic foxes was found. Arctic foxes infected with 1000 T. leonine eggs had minimal body weight gain and lower fur quality, resulted in a lower pelt price. The analysis of the effects of T. leonina infection on the course of pregnancy has shown that toxacariasis causes 5 % of all abortions in arctic foxes and 9 % (P>0.99) of cases of cannibalism. The results obtained suggest that the hostparasite system Alopex lagopus – T. leonina has a wide range of adaptation possibilities. Low intensity infection with T. leonina does not have a pronounced pathological effect on the body weight and fur quality. It is also not a major cause of abnormal pregnancy, but aggravates it. Higher infection dose, 1000 eggs/host affects the established relationship and shifts the balance in host-parasite relations to the detriment of the host. Decrease in the body weight negatively affects pelt size and quality.