The possible mode of action of Etodolac, a potent anti-inflammatory drug, has been investigated. The effect of Etodolac on macrophage inflammatory depressed the influx of inflammatory macrophages into peritoneal cavity following stimulation with a sterile irritant. This decrease in macrophage accumulation in vivo correlated with the effect of Etodolac on the macrophage chemotaxis in vitro. Etodolac was also capable of reducing the macrophage ability to migrate towards a chemoattractant. In vivo Etodolac should reduce the amount of damage produced at the site of chronic inflammation since fewer macrophages would migrate to the inflammatory sites.