gas chromatography-mass spectrometry (gc-ms) analysis of aloysia gratissima (gill. et hook) tronc. essential oil obtained by hydrodistillation lead to the identification of twenty-two compounds. the major compounds found in this study were 1,8-cineole (13.7%), germacrene d (13.4%), -caryophyllene (12.7%) and -pinene (11.7%). the oil demonstrated antibacterial and antifungal activities against mainly bacillus cereus and trichophyton mentagrophytes. aloysia gratissima oil was also screened for its antioxidant activity by 2,2-diphenylpicrylhydrazyl (dpph) free radical; however, it was less effective than butylated hydroxytoluene (bht). these findings suggest feasible application of a. gratissima essential oil as an antimicrobial agent and its chemical characteristic may lead to the extraction of active compounds in isolated or combined forms with useful applications.