Gypsy moth 4 th instar caterpillars were fed for 3 days with an artificial diet supplemented with increasing cad-mium (Cd) concentrations (0, 10, 30, 100 and 250 µg⁄g of dry food weight). Changes in the morphometric characteristics of A1' dorso-medial and L2 dorso-lateral neurosecretory neurons (nsn) were analyzed. In the A1' nsn, Cd supplements led to an enhanced nuclear size, except in the group treated with 250 µg Cd⁄g in the form of dry food. The size of L2 type nsn was increased in the groups provided with 30 and 100 µg Cd⁄g, while no differences in the size of nuclei was detected in L2 neurons among the experimental groups.