In an experiment with white nubilous male rats the morphofunctional state of neurons in the cerebral hemisphere cortex was evaluated with the morphological and statistical methods following electromagnetic exposure (500 impulses once a week for 5, 7 and 10 mos.) inducing in the animal body the averaged current densities of 0.21 and 1.5 kA/m2. Chronic exposure to electromagnetic fields with the density of 0.21 kA/m2 was found to increase the biosynthetic activity of neurons by way of compensation and adaptation and level at the end of experiment, whereas the density of 1.5 kA/m2 brings about profound structural and functional disorders in and inhibits the biosynthetic activity of the neurons.