In vertebrates, the integrin family includes 24 members. As the alpha-chains were sequenced, some were observed to have an inserted domain similar to the A domain in several matrix and complement proteins. This inserted ligand binding domain is interactive and was called the I domain in integrins. More recently structural data have shown that an integrin beta-chain also contains an I domain. Nine of the currently known 18 alpha-chains contain an I domain. This book systematically goes through the current knowledge about these integrins, including the newest additions to the integrin family, the collagen-binding alpha10beta1 and alpha11beta1 integrins. The book discusses ligand binding, signalling properties, knock-out phenotypes and possible involvement in disease. This book comprehensively reviews the current knowledge about I domains in integrins and will serve as a useful reference book for scientists in this field.