Nectins have recently been identified as new cell adhesion molecules (CAMs) consisting of four members. They show immunoglobulin-like structures and exclusively localize at adherens junctions (AJs) between two neighboring cells. During the formation of cell-cell junctions, nectins function in cooperation with or independently of cadherins, major CAMs at AJs. Similar to cadherins, which are linked to the actin cytoskeleton by binding to catenins, nectins also bind to afadin through their C-terminal region and are linked to the actin cytoskeleton. In addition to nectins, there are nectin-like molecules (Necls), which resemble nectins in their structures and consist of five members. Nectins and Necls are involved in the formation of various kinds of cell-cell adhesion, and also play key roles in diverse cellular functions including cell movement, proliferation, survival, and differentiation. Thus, nectins and Necls are crucial for physiology and pathology of multicellular organisms.(Communicated by Shigetada NAKANISHI, M.J.A.).