The cytotoxic activity of nine terpenoids and flavonoids isolated from Artemisia annua was tested in vitro on several human tumor cell lines. These compounds are artemisinin, deoxyartemisinin, artemisinic acid, arteannuin-B, stigmasterol, friedelin, friedelan-3 beta-ol, artemetin, and quercetagetin 6,7,3',4'-tetramethyl ether. Friedelane-type triterpenoids were isolated for the first time from this plant. Artemisinin and quercetagetin 6,7,3',4'-tetramethyl ether showed significant cytotoxicity against P-388, A-549, HT-29, MCF-7, and KB tumor cells.