The five integrins that contain the αv subunit are widely expressed and their expression is tightly regulated. However, most tissues in mice lacking the αv subunit, and thus deficient in all five integrins, develop normally, suggesting that nearly all of the critical steps in development and cellular differentiation can occur in the absence of these integrins. Studies over the past few years have identified highly specialized roles for specific αv integrins in preventing inappropriate vascular growth and in control of vascular permeability. Two members of this family, αvβ6 and αvβ8, play novel roles in activating latent complexes of the growth factor TGFβ (transforming growth factor β). Studies in mice lacking the β6 subunit have identified unexpected roles for αvβ6-mediated TGFβ activation in models of pulmonary and renal fibrosis, acute lung injury and pulmonary emphysema.