The intraperitoneal injection of glycogen in the mouse resulted, shortly thereafter, in the accumulation of 14-23 million neutrophils in the peritoneal cavity and a four-fold increase in the numbers of circulating neutrophils. Preceding the influx of leukocytes, the exudation of plasma proteins and the chemotactic activity for mouse neutrophil in vitro increased in the peritoneal fluid. Among various protease inhibitors examined, chymostatin alone suppressed the plasma protein exudation. Indomethacin and dexamethasone reduced the accumulation of white cells and protein exudation. These nonsteroidal and steroidal antiinflammatory drugs were equally effective whether given simultaneously with or 60 min before glycogen or whether administered intraperitoneally or orally. Colchicine showed a suppressive effect on the leukocyte accumulation but enhanced the protein exudation.