The receptors that mediate monocyte adhesion to cytokine-stimulated endothelial monolayers were assessed using a nonstatic (rotating) cell-attachment assay. In this system, leukocyte adhesion molecule-1 (LAM-1) (L-selectin) mediated a major portion (87 +/- 15% at 37 degrees C) of monocyte attachment to activated endothelium. mAb blocking of endothelial leukocyte adhesion molecule-1 (41% inhibition), CD18 (36%), and vascular cell adhesion molecule-1 (25%) function had lesser effects on attachment. These results suggest that LAM-1 may serve an important role in monocyte attachment to endothelium at sites of inflammation.