Cell-cell and cell-matrix adhesions play important roles in determining the structural organization and behaviour of cells in tissues. These adhesions are mediated by specific cell-surface receptors that are linked to the actin cytoskeleton through submembranous multiprotein complexes that also serve to generate intercellular signals. The molecular mechanisms by which regulation of cell adhesiveness is coordinated with other aspects of cell behaviour are now under study and some aspects of this are highlighted in this short review. New scope for analysis of the roles of individual adhesion molecules in vivo is being provided by mouse gene knockouts.