Objective To monitor the sensitivity of Plasmodium falciparumto artemisinin derivatives in order to allow rational use of antimalarials. Methods Microplates and medium for field used were successfully prepared and then an in vitro micro assay recommended by the WHO was used to ascertain the sensitivity of P.falciparumto artesunate,dihydroartemisinin,artemether,and arteether. Results In Ledong County,Hainan Province,the mean concentration of artesunate for complete inhibition of schizont formation increased ...