Chemokines control inflammatory leukocyte recruitment. The propensity of chemokines such as CC chemokine ligand 5 (CCL5)/RANTES (regulated on activation, normal T cell expressed and secreted) to bind to glycosaminoglycans and to form higher order oligomers has been shown to be essential for its in vivo activity. However, the specific functional relevance of RANTES oligomerization for distinct steps of leukocyte recruitment on inflamed endothelium mediated by the RANTES receptors CC chemokine receptor 1 (CCR1) and CCR5 remains undefined. We studied RANTES mutants with deficient oligomerization in an assay in which recruitment of monocytes and CD45RO+ CD4+ T cells is triggered by RANTES immobilized on activated endothelium under flow conditions. Notably, the formation of higher order RANTES oligomers was crucial for CCR1-mediated arrest but not for CCR5-mediated spreading/transmigration in flow or transendothelial chemotaxis of leukocytes. Efficient leukocyte arrest in flow but not transmigration may thus require the presentation of RANTES oligomers to bridge surface-bound RANTES and CCR1.