The effect of cadmium on the establishment of host_parasite interactions, particularly, on the hatching of potato cyst nematode invasive juveniles was experimentally studied. Application of a logistic model allowed us to reveal the influence of the tested substances at all stages of the nematode hatching process. It was shown that cadmium ions speeded up the period of the most active juvenile emergence from cysts. In the control 50% of juveniles hatched by the 18th day, in the experiment they emerged early (by the 14th day). The parasite benefited from the shortening of this stage as it could sooner penetrate the host roots and raise the infestation level of the plants in the cadmium_contaminated fields.