This review systematically analyses recent knowledge of the biology of somatostatin receptors. Indeed, since the molecular cloning of five somatostatin receptors in 1992, a growing bulk of scientific data has been produced regarding the cell type localization, the physiological role and the biochemical intracellular pathways activated by the single somatostatin receptors. The aim of this review is to present all these data, also discussing the conflicting evidence that has been reported, to further simulate research efforts in the field.