Interest in the biological aspects of panic disorder has been focussed mainly on the noradrenergic and serotonergic systems in the brain. Recently evidence has been found that Cholecystokinin (CCK) receptors in the Central Nervous System (CNS) may be involved in panic disorders. This hypothesis is based on the results of animal electrophysiological studies, animal models of anxiety and on challenge test using CCK fragments in humans. In this review, the studies evaluating the putative involvement of CCK, and especially CCK-B receptors, in panic disorder will be discussed.