A new compound, named jiangxienone, has been isolated from a culture of the traditional Chinese medicinal mushroom Cordyceps jiangxiensis, and its chemical structure was established on the basis of spectroscopic and chemical techniques. Jiangxienone showed potent cytotoxic effects against human gastric adenocarcinoma SGC-7901 cell and human lung carcinoma A549 cell with IC(50) values ranging from 1.38 to 2.93 μM, i.e., with at least approximately six-fold stronger cytotoxicity than cisplatin, a first-line chemotherapy drug for cancer patients., (Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zürich.)