Licochalcone A, a compound isolated from Chinese liquorice roots, inhibited the in-vitro growth of a chloroquine-sensitive (3D7) and a chloroquine-resistant (Dd2) isolate of Plamodium falciparum to a similar extent. When licochalcone A was added to highly synchronised cultures containing mostly rings, trophozoites or schizonts, the growth of all these asexual stages of the parasites was found to be inhibited. When the compound was administered either intraperitoneally or orally for up to 6 days to mice infected with P. yoelii, it protected the rodents from the otherwise lethal infection. In preliminary toxicity studies in rats, oral doses up to 1000 mg licochalcone A/kg body weight did not cause any observable toxicity. Licochalcone A therefore exhibits potent antimalarial activity and shows promise as a potential, new antimalarial drug.