A number of monoclonal antibodies (Mab) specific to human leukocyte adherence molecules were investigated for their possible function in LA-CMI assay. These data indicate that LFA-1 appears to be directly involved in LA-CMI of human peripheral blood leukocytes since both MAb H52, specific to LFA-1 beta and MAb MHM24, specific to LA-1 alpha inhibited LA-CMI that retained distinct functional characteristics normally exhibited in LFA-1-dependent adhesion steps. That is, binding of cells onto tube wall required the presence of bivalent cations and metabolic energy production; it could be stimulated by phytohemagglutinin (PHA) and was partially dependent on intact cytoskeleton and temperature. MAbs specific to other adherence molecules such as ICAM-1, CD2, CD58, CD4, CD8, CD11b and LAM-1 did not affect leukocyte adherence in this model.