The adhesion of leukocytes to glass beads in protein-free media was quantitatively high and not dependent on divalent cations. Addition of plasma, albumin or gelatin in increasing concentrations gradually reduced leukocyte adhesion, which then became increasingly dependent on divalent cations. Heat inactivation of plasma did not affect leukocyte adhesion. Leukocyte migration in glass capillary tubes, which was dependent on a heat labile plasma factor, was promoted by each of the proteins listed and by siliconizing the tubes. Leukocyte migration in millipore filters was enhanced when albumin was present in the cell starting compartment. Lidocain reduced both leukocyte adhesion to protein-coated glass and leukocyte migration in capillary tubes and millipores filters. Ethanol reduced leukocyte adhesion and leukocyte filter migration. E. coli endotoxin enhanced adhesion of leukocytes but inhibited their migration in tubes and filters. The findings indicate the existence of a relationship between adhesion and migration of leukocytes.