Abstract: Objective To establish an in vitro microtest for determining the sensitivity of Plasmodium falciparum to pyronaridine Methods Pyronaridine-coated plate and culture medium which is easy to use in the field were prepared. P.falciparum parasites from in vitro continuous passage culture（FCC1/HN） were used for experimental tests in the laboratory. When they were proved stable and reliable through repeated determinations， field trials were made in Hainan and Yunnan Provinces during the malaria transmission season with blood samples from clinical falciparum malaria cases. A 4-week in vivo test was carried out as a control. Results The pyronaridine-coated plate and culture medium were proved to be stable. The effective period of pyronaridine-coated plate， the ampule sealed liquid culture medium and the bottled lyophilized culture medium， all stored at 4 ℃ was 6 months， 2 months and 2 years respectively. Through several years field determinations， the baseline data of pyronaridine-sensitivity of P.falciparum in the country were collected and the sensitivity of P.falciparum to pyronaridine was also revealed to have decreased gradually. The mean drug concentration for in vitro complete inhibition of schizont formation raised by 2-4 times although the clinical therapeutic efficacy of pyronaridine was still satisfactory at the present time. Conclusion The developed in vitro microtest can be used for determination of the sensitivity of P.falciparum to pyronaridine， and it is more convenient and sensitive than the 4-week in vivo method.

Key words: Plasmodium falciparum, Pyronaridine, Sensitivity, In vitro microtest