Serotonin (5-HT) is involved in various physiological and pathological processes by interaction with 14 distinct receptor subtypes, grouped in seven classes of receptors (5-HT(1-7)) on the basis of amino acid sequence, pharmacology, and signal transduction pathways. The 5-HT(7)R is a G-protein coupled receptor with seven transmembrane domains. It was found by the application of molecular cloning and has been identified in rat, mouse, human, pig, and guinea pig. Although the biological functions of the 5-HT(7)Rs are poorly understood, preliminary evidence suggests that it may be involved in depression, control of circadian rhythms, and relaxation of vascular smooth muscles. For these reasons, the 5-HT(7)R has become a target for the development of novel drugs. This review will give a brief introduction of the pharmacology of 5-HT(7)R (molecular structure, distribution of 5-HT(7)R mRNA, localization of the 5-HT(7)R protein, functional correlates, and therapeutic potential) and a detailed survey of the 5-HT(7)R ligands, which have appeared in the literature in both papers and patents. Structure-activity relationships (SAR) of these ligands will also be described.