Cadherins are a family of membrane receptors that mediate calcium-dependent homophilic cell-cell adhesion. Cadherins play a key role in the regulation of organ and tissue development during embryogenesis. In adult organisms, these proteins are responsible for formation of stable cell-cell junctions and maintenance of normal tissue structure. Disruption in expression or function of cadherins may cause uncontrolled cell migration and proliferation during tumor development. This review focuses on the structure and physiological functions of classical cadherins.