A number of studies have been carried out over the past year to characterise the physiological functions and possible therapeutic applications of somatostatin (sst). Somatostatin is one of the most widespread peptides in the body and it fulfils a very wide spectrum of actions in the various organs and tissues. The aim of this review is to make a critical analysis of knowledge of the structure and physiology of sst and its receptors, together with the possible role played by this peptide in cell proliferation in animal models and the treatment of human tumours. In particular, the authors discuss the most recent findings on cell and intracell mechanisms regulated by somatostatin receptors and how this knowledge may encourage the development of more effective and selective new molecules in terms of therapy.