Studies of the protective actions of three doses of delta-sleep-inducing peptide (DSIP) given at different times before barochamber compression of animals to an oxygen tension of 0.7 MPa showed that the optimum DSIP dose is 12 μg/100 g. Intraperitoneal administration of this dose of DSIP delayed the onset of generalized convulsive activity by a factor of 2–2.5 in animals exposed to an oxygen tension of 0.7 MPa and promoted normalization of the sleep-waking cycle within 24 h after exposure to hyperbaric oxygen (HBO), by creating an optimal balance between excitatory and inhibitory amino acid neuromediators.