The aqueous and hydro alcoholic extracts of Artemisia annua plants acclimatized and set in culture in Benin, were investigated for their in vitro and in vivo antimalarial value. These extracts were prepared by decoction and maceration using water and ethanol, and were tested for in vitro activity against the strains of Plasmodium falciparum. Those extracts were also investigated in vivo against Plasmodium berghei NK 173 infected mice by the 4-day suppressive test. The action of these extracts was similar in vitro to the action of pure artemisinin at the same dosage. But, the in vivo studies on mice show that we have the same efficacy with aqueous extract of A. annua (artemisinin content of 20 mg/kg) than with pure artemisinin at a dosage of 140 mg/kg. The hydro alcoholic extract of A. annua (artemisinin content of 20 mg/kg) was better than the both other conditions. The others components of the plant Artemisia annua potentiate artemisinin activity on Plasmodium. The aqueous and hydro alcoholic extracts of Artemisia annua L. are very effective on malaria and they can be used by populations to cure this disease, especially in endemic areas where modern medicines are expensive.