aloysia gratissima is used in popular medicine as an analgesic and sedative. however, studies on its biological activities are still scarce. therefore, this work aimed to evaluate the antinociceptive and anti-inflammatory effect of a. gratissima leaves essential oil (oag) in mice. the oag was obtained by hydrodistillation and its composition was determined by gas chromatography-mass spectrometry. the sesquiterpenes pinocamphone, - pinene, and guaiol were the major constituents of oag. the effect of oag (1, 10, and 30 mg/kg, p.o.,) was assessed by pre-treating male mice 1h before the formalin assay, carrageenan-induced peritonitis test, or the paw edema induced by arachidonic acid (aa). the acute toxicity of oag (2000 mg/kg, p.o.) was also investigated. the minimum effective dose of oag in the formalin test was 1 mg/kg. this dose did not affect the locomotor activity of mice. the oag decreased the number of leukocytes/mm^3 in the peritoneal exudate of mice and reduced paw edema 45 min after the arachidonic acid injection. oag treatment elicited a reduction in npsh levels in the paw tissue and increased npsh levels in mice blood plasma and did not cause mice mortality. the oag is devoid of acute toxicity and shows anti-inflammatory activity, which can be related to the presence of pinocamphone, guaiol, and - pinene and is mediated, at least in part, by mechanisms that involve the participation of npsh.