The major falvonoid constituents of the Antarctic grass, Deschampsia antarctica, are shown to be the C-glycosylfavones, isoswertiajaponin (7-O-methylorientin) 2''-O-beta-arabinopyranoside and orientin. These are accompanied by lower levels of orientin 2''-O-arabinopyranoside, isoswertisin (7-O-methylvitexin) 2''-O-beta-arabinopyranoside, acylated derivatives, isoswertisin, isoswertiajaponin and tricin. A preliminary study suggests that the overall level of flavonoids in Deschampsia increases during the Antarctic mid-summer.