DHB [2,3-dihydroxybenzoic acid] potentiated [human] PMN [polymorphonuclear leukocyte] phagocytosis of opsonized lipopolysaccharide-coated PO [paraffin oil] droplets by 53-45% and chemotaxis by 36-10% at 10-3 M and 10-4 M concentrations, respectively. The effect was reversible in vitro. With DHB, PMN released significantly less superoxide and H2O2 to the extracellular media but were able to oxidize 1-14C-glucose normally during phagocytosis. Although iodination of opsonized particles was decreased with DHB, the PMN were able to kill Staphylococcus aureus 502A normally. Directed cell movement and phagocytosis may be enhanced by protecting the PMN membrane against auto-oxidative damage from scavenging superoxide and H2O2 by DHB.