Human polymorphonuclear leukocytes were incubated with either methylprednisolone sodium succinate, hydrocortisone sodium succinate, or distilled water, and then latex spherules were added as target particles for phagocytosis. At low concentrations of these corticosteroids (0.04-0.22 mM), no effect was observed on O2-. production, H2O2 production, or chemiluminescence. At high concentrations of these steroids (2.7 mM), a significant inhibition was observed in both O2-. production and H2O2 production. At 2.7 mM, methylprednisolone sodium succinate significantly decreased chemiluminescence, whereas hydrocortisone sodium succinate was without effect on chemiluminescence.