The advent of in situ immunology and intravital analyses of leukocyte movement in tissues has drawn attention to the previously neglected extracellular matrix (ECM) and its role in modulating immune cell behaviour in inflamed tissues. The ECM exists in different biochemical and structural forms; both their individual components and three-dimensional ultrastructure impart specific signals to cells that modulate basic functions that are important for the early steps in inflammation, such as immune cell migration into inflamed tissues and immune cell differentiation. In chronically inflamed tissues, aberrant ECM expression and fragments of the ECM that are derived from tissue-remodelling processes can influence immune cell activation and survival, thereby actively contributing to immune responses at these sites.