The results of the present study showed that the essential oil from the fresh rhizome of C. aeruginosa was rich in oxygenated sesquiterpenes, i.e. germacrone. With regard to the scavenging ability to DPPH and OH radicals, the essential oil showed strong antioxidant activity as compared with L-ascorbic acid. In addition, the essential oil exhibited strong inhibitory activity against E. faecalis ATCC 29212, but gave weak inhibitory activity against M. tuberculosis strain H37Ra. This is the first report of antimycrobacterial activity of essential oil from the fresh rhizome of C. aeruginosa. The results suggest that the essential oil from the fresh rhizome of C. aeruginasa might be a potential source of natural antioxidant and antibacterial substances.