Integrins are heterodimeric cell adhesion molecules that link the extracellular matrix to the cytoskeleton. The integrin family in man comprises 24 members, which are the result of different combinations of 1 of 18 alpha- and 1 of 8 beta-subunits. Alternative splicing of mRNA of some alpha- and beta-subunits and postranslational modifications of integrin subunits further increase the diversity of the integrin family. In their capacity as adhesion receptors that organize the cytoskeleton, integrins play an important role in controlling various steps in the signaling pathways that regulate processes as diverse as proliferation, differentiation, apoptosis, and cell migration. The intracellular signals that lead to these effects may be transduced via cytoplasmic components, which have been identified as integrin-binding proteins in yeast two-hybrid screens and which could mediate the coupling of integrins to intracellular signaling pathways. In this review an overview is given of the function and ligand-binding properties of integrins as well as of proteins that associate with integrins and may play a role in their signaling function.