The nectin family comprises four Ca(2+)-independent immunoglobulin-like cell-cell adhesion molecules. Each nectin homophilically and heterophilically trans-interacts and causes intercellular adhesion, which organizes a variety of intercellular junctions in cooperation with, or independently of, cadherin. Nectin furthermore induces activation of Cdc42 and Rac small G proteins through c-Src, which eventually regulates formation of the cadherin-based adherens junctions through reorganization of the actin cytoskeleton, gene expression through activation of a mitogen-activated protein kinase cascade, and cell polarization through cell polarity proteins. We describe here the roles of nectin in intracellular signaling.