Integrins - heterodimeric cell-surface receptors that bind to laminin,collagen and other ligands in the extracellular matrix (ECM) - propagate many intracellular signals during development. For example, integrin-ECM interactions regulate the formation of new blood vessels (angiogenesis). But which integrin-ligand pairs are required in endothelial cells (ECs) to mediate this process? Carlson and co-workers now report that β1 integrin is needed for EC adhesion, migration and survival during angiogenesis (see p. 2193). Lineage-specific deletion of Itgb1 (which encodes β1 integrin)in ECs in mouse embryos causes embryonic lethal vascular defects, they report,including the formation of a discontinuous endothelium in blood vessels. Furthermore, isolated Itgb1-null ECs behave in a disorganised manner,fail to adhere to or migrate on laminin or collagen substrata and have reduced survival. These findings highlight the essential role that β1 integrin plays during angiogenesis and suggest that targeted therapies that block the function of β1 integrins in ECs could control the growth and survival of cancers by preventing neovascularisation.