Two types of opioid receptors were studied in the brain of rats: Delta (for endogenous opiate) and mu (for exogenous opiates). 3H derivates: D-Ala2-enkephalin and Naloxone were used as labeled ligands. The results obtained were calculated by computer program for automatic estimation of the data using approximation equations. An increase of binding delta receptors is observed in both types of stress (2-8 times), while to the mu receptors the binding is less effective mainly after irradiation. These data suggest that a close interaction exists between sympathoadrenal system and opioid mechanisms during stress.