Fixed oil of O. basilicum was found to possess significant antiinflammatory activity against carrageenan and different other mediator-induced paw edema in rats. Significant inhibitory effect was also observed in castor oil-induced diarrhoea in rats. It also inhibited arachidonic acid- and leukotriene-induced paw edema. The results of antiinflammatory activity of O. basilicum support the dual inhibition of arachidonate metabolism as indicated by its activity in inflammation models that are insensitive to selective cyclooxygenase inhibitors. On the basis of these findings, it possible to conclude that O. basilicum may be a useful antiinflammatory agent which block both cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism.