Five groups of ten male Wistar rats each were used for the purpose of this experiment. All subjects suffered from sterile acute inflammation in the peritoneal cavity. A sterile beef heart infusion broth reinforced with proteose-peptone was injected to cause the inflammation. The following substances mixed with tragacanth gum were given orally at in 12 h intervals: --Acetalsalicylic acid 150 mg/kg body weight to the first group; --Phenylbutazone 100 mg/kg body weight to the second group; --Indomethacin 15 mg/kg body weight to the third group; --Flufenamic acid 100 mg/kg body weight to the fourth group. Finally the fifth group received only tragacanth gum. The rats were sacrificed after 48 hours and leucocytes were collected from the peritoneal cavity by washing with 5 ml 0.9% NaCl solution. The total leucocyte number and the percent of each type were estimated for each group individually. A statistically significant decrease in the number of leucocytes migrated to the peritoneal cavity due to the inflammation was observed in rats that received one of the drugs (group I to IV) when compared to rats that received only the excipient (group V). Likewise, significant differences were noted in the composition of each type.