The effects of the calcium channel blockers S- and R-verapamil or Ro 40-5967 on penetration processes of peripheral blood lymphocytes (PBL) added to allogenic human vascular endothelial cell (HUVEC) monolayers were studied. Both PBL adhesion and migration were evaluated by combined phase contrast and reflection interference contrast microscopy. PBL adhesion was inhibited by 22% when 100μg/ml verapamil was added to the cell cultures. PBL migration was completely suppressed with verapamil concentrations above 80μg/ml (EC50: S-verapamil: 59.7μg/ml, R-verapamil: 52.3μg/ml). No differences were seen in the results obtained either with or without cytokine (γ-IFN or IL-1) stimulation. Ro 40-5967 redlfced adhesion completely above concentrations of 40μg/ml. EC50for migration was 13±2 or 13±1μg/ml, respectively. Immunohistochemical analysis of adhesion molecule expression on HUVEC revealed no inhibition of 1CAM-1 and VCAM-1 by verapamil or Ro 40-5967. We concluded that the effects of the calcium channel blockers did not depend on cytokine stimulation and, as they were found similar for both verapamil enantiomers, also did not depend on the calcium channel blocking properties of the compounds. Since adhesion molecule expression was not reduced on HUVEC the Ca2+-channel blockers tested in this assay seem to affect cellular infiltration via other pathways.