It has been known that ciprofloxacin augments the humoral and cellular immune systems. The aim of the present study was to determine whether these properties affect the inflammatory response. Adult male rats, ciprofloxacin and pefloxacin were used. The healty rats were treated orally with an equal volumes of ciprofloxacin (50 mg/kg) pefloxacin (50 mg/kg) or distilled water for 10 days. Their effects on the inflammatory response were investigated by testing the formation of formaline-induced edema. The effects of two quinolones were also evaluated on gastic mucus secretion by using the Alcian blue dye binding method and haematological parameters. Ciprofloxacin and pefloxacin showed a significant antiinflammatory activity and decreased the white blood cell count (WBC). However, there was no significant difference in the other haematological parameters. These two quinolones stimulated gastric mucus secretions, but these increases were not statistically significant. These findings suggest that ciprofloxacin and pefloxacin (at 50 mg/kg p.o. doses) possess antiinflammatory activities and are well-tolerated orally. Further detailed investigations are needed to clarify the mechanisms of their antiinflammatory activities.