[Fluctuation in the resistance of Plasmodium falciparum to chloroquine in China].

Objective: To investigate whether chloroquine-resistance of Plasmodium falciparum had changed after stopping or reducing the use of chloroquine as an antimalarial in Hainan and Yunnan provinces.

Methods: WHO standard in vitro microtest and 4-week in vivo test were used, assays were carried out in different time after stopping or reducing the use of chloroquine.

Results: In vitro test in Hainan indicated that the rate of chloroquine-resistant P.