Trichilia glabra L. aqueous leaf extract exerted a significant antiinflammatory effect 'in vivo' in the zymosan-induced inflammation model. The extract impaired the 'in vitro' activities of polymorphonuclear leukocytes and complement, components of mouse immune system closely related to the inflammatory response induced by zymosan. In particular, a significant reduction in the phagocytic capability and respiratory burst response of mouse polymorphonuclear leukocytes together with an inhibition in the hemolytic activity of mouse complement was observed.