Adhesion of human polymorphonuclear leucocytes (PMN) stimulated with phorbol myristate acetate (PMA) to plastic dishes coated with the matrix proteins laminin (LM), fibronectin (FN), collagen type I (CI) or collagen type IV (CIV) was inhibited by the monoclonal antibody 60.3 (MoAb 60.3; anti-CD18). The highest inhibitory effect was seen on adhesion to CI. PMN adhesion to CI was also effectively inhibited by Mo1 (anti-CD11b) but this antibody had only a minor effect on attachment of PMN to the other matrix proteins. In other experiments MoAb 60.3 inhibited LTB4-induced migration of PMN through polycarbonate filters (3 microns pores) coated with LM, FN, CI or CIV, with the most pronounced effect on migration through those filters coated with CI. By contrast, the antibody Mo1 had no effect on migration through any of the protein-coated filters tested. The results in this study suggest that the CD18 epitope, recognized by 60.3, mediates both adhesion and migration of PMN while the epitope on CD11b recognized by the antibody Mo1 is restricted to adhesion. The results also indicate that CD11b/CD18 is the major receptor on human PMN for CI while interaction with LM, FN and CIV may in addition involve other mechanisms.