We have examined the inhibitory effect of monoclonal antibodies against mouse P-, E- and L-selectin on the migration of neutrophils into the chemically inflamed peritoneum of the mouse. For this purpose; monoclonal antibodies were raised against mouse P- and E-selectin, which block cell adhesion. We found that blocking of each selectin alone inhibited neutrophil migration to a similar degree ranging from 63% to 72%. Of the three possible combinations of antibodies against two different selectins only the combination of anti-P- and anti-L-selectin antibodies caused an essentially complete blockade of neutrophil emigration. Only the effects of these two antibodies were additive, while the effect of anti-E-selectin antibodies did not add to the effect of antibodies against P- or L-selectin. Thus, although E-selectin is involved in neutrophil migration into the inflamed peritoneum of the mouse, it cannot compensate the block of the other two selectins which seem to play the dominant role in this process.