Members of the integrin family recognize a variety of spatially-restricted extracellular ligands. Classically, ligation of integrins activates cytoplasmic signals in the integrin-expressing cell and contributes to cell adhesion, migration, proliferation and survival. At least two members of this family, αvβ6 and αvβ8 perform an additional function, activation of latent complexes of transforming growth factor β. In effect, this process allows integrins on one cell to activate signals on adjacent (in the case of αvβ6) or nearby cells (in the case of αvβ8). Integrin-mediated TGFβ activation has been shown to play important roles in modulating tissue fibrosis, acute lung injury and pulmonary emphysema. Given the important roles that TGFβ plays in modulating epithelial cell growth, epithelial-to-mesenchymal transformation and tumor invasion and metastasis, integrin-mediated TGFβ activation is likely to play important roles in tumor growth ad metastasis.