Serotonin (5-hydroxytryptamine, 5-HT) is one of the most attractive targets for medicinal chemists. Among 5-HTRs, the 5-HT 1A subtype is the best studied and it is generally accepted that it is involved in psychiatric disorders such as anxiety and depression. Several structurally different compounds are known to bind 5-HT 1A R sites. Among these, arylpiperazine derivatives represent one of the most important classes of 5-HT 1A R ligands. This article will review the development of arylpiperazine derivatives acting at 5-HT 1A Rs with an emphasis on structure-affinity relationships of agonists and antagonists, ligand-receptor interactions and pharmacological applications.