There has been no information on cystogenous nematodes of the genus Heterodera injuring apple trees. The paper checks the first finding of these nematodes on the roots of a cultivated apple tree. The nematodes proved to be a new species, Heterodera mali sp. n. The apple cystogenous nematode resembles the potato cystogenous nematode H. rostochiensis Woll. in having a round body, small cleft of the vulva and similar sizes of eggs. It differs from H. rostochiensis in smaller sizes (on the average 5 against 9) very transparent and thin cuticle, a small distance between vulva and anus (on the average 43 against 86), a smaller value of the Granek's index (on the average 1.3 against 4.6), a smaller number of cuticular folds between vulva and anus (on the average 7 against 21) and different plant-hosts. A detailed description of H. mali sp. n. is given.