Chemokines are small proteins that have an important function in the trafficking of immune cells. Platelets also contain chemokines, which are stored in the alpha-granula. Activated platelets are able to deposit chemokines onto inflamed endothelium via transient rolling interactions, thereby enhancing subsequent arrest of e.g. monocytes. The chemokines RANTES/CCL5 and platelet factor 4 (PF4/CXCL4) are deposited by platelets and can form heteromers. These CCL5/CXCL4 heteromers are particularly potent as monocyte attractant. This protocol describes the precipitation of the CCL5/CXCL4 complex from platelets.