Introduction of phytoecdysteroids (ecdysterone, turkesterone and ñyasterone) to rats subjected to prolonged immobilization stress significantly decreased involution of the thymus and spleen, contributed to normalization of increased mass of adrenal glands, and restored their content of ascorbic acid and cholesterol. In the liver of stressed animals, phytoecdysteroids prevented sharp decrease in the glycogen concentration, showed a clear trend toward normalization of the ratio of lactic and pyruvic acids, maintained homeostasis of macroergic phosphorus compounds, and increased the activity of antioxidant enzymes that inhibit lipid peroxidation. With respect to the stress-protective activity, the studied phytoecdysteroids are in some cases superior to eleutherococcus extract.