Cell cycle progression in mammalian cells is strictly regulated by both integrin-mediated adhesion to the extracellular matrix and by binding of growth factors to their receptors. This regulation is mediated by G₁ phase cyclin-dependent kinases (CDKs), which are downstream of signaling pathways under the integrated control of both integrins and growth factor receptors. Recent advances demonstrate a surprisingly diverse array of integrin-dependent signals that are channeled into the regulation of the G₁ phase CDKs. Regulation of cyclin D1 by the ERK pathway may provide a paradigm for understanding how cell adhesion can determine cell cycle progression.