We used immunocytochemical methods to identify activated endothelial cells and the ligands of infiltrating cells in sural nerve biopsies from 30 patients with peripheral neuropathy. In chronic inflammatory demyelinating polyneuropathy (CIDP), the endothelial leukocyte adhesion molecule (ELAM-1; E-selectin) was detected in the epineurial vessels of five of the 10 patients. CD68-positive monocytes were usually at ELAM-1-positive endothelial sites and in perivascular tissues, while sialyl-Lewis x-positive cells were detected mostly in the lumina adherent to ELAM-1-positive endothelial cells. The location of activated T cells was not correlated with activated endothelial cells, and endoneurial vessels were not immunostained for ELAM-1. In view of the transient expression of ELAM-1 in response to cytokine stimulation, these findings suggest that endothelial cells play a role in the extravasation of infiltrating cells in CIDP.