Specific chemokines and chemokine receptors have been implicated in inflammatory demyelinating diseases of the central nervous system (CNS), including multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). Amino-terminal modifications of chemokines can alter receptor interactions, converting agonists to specific antagonists. To examine the function in EAE of murine types 1 and 5 CC chemokine receptors (CCR1 and CCR5), we used Met-RANTES, a peptide that blocks both receptors; controls received heat-inactivated peptide. There was no effect of active treatment on acute-monophasic EAE, regardless whether compound was given at onset or in a pre-treatment regimen. Administered at disease onset, Met-RANTES modestly but significantly ameliorated fixed neurological disability at the endpoint of chronic-relapsing EAE. Met-RANTES treatment did not reduce CNS cellular infiltrates or up-regulation of CCR1 and CCR5 in affected CNS tissues. Analysis of a subset of mice suggested a trend towards reduced axonal pathology in those receiving active treatment. These data indicate that chemokine receptor blockade with Met-RANTES does not affect leukocyte trafficking in chronic-relapsing EAE. Further analysis of the effects of chemokine receptor blockade may need to focus on leukocyte activation within the affected CNS as well as trafficking events.