Analogues of the endogenous peptide corresponding to the 30-33 sequence of cholecystokinin (Trp-Met-Asp-Phe-NH2) were synthesized, and their biological activity was studied. It was shown that, in rats, the N-succinylated Nle2 analogue of this tetrapeptide exhibits increased anxiolytic properties in the dark-bright chamber test and an enhanced alcohol intake by both the control animals and the long-time alcohol-dependent animals under the conditions of free choice. Introduction of an isopropyl residue into the C-terminal amide of the Nle2 analogue resulted in the appearance of anxiolytic and antialcohol activity and the ability to increase the morphine analgesic effect in the tail-flick test on rats. The two synthesized analogues retained an affinity to cholecystokinin receptors.