Abstract: The sensitivity of Plasmodium falciparum to piperaquine and the gametocidal effect of the combination of piperaqune with primaquine were studied in Baoting, Hainan where piperaquine has been used for ten years. The results suggested that the sensitivity of P. faldparum to piperaquine was almost the same as that reported ten years ago. However, after the piperaquine treatment gametocytocemia occurred in 40% of the patients. These gametocytes could be eliminated completely by a single dose of 45mg primaquine within 2-4 days (on an average of 2.8 days). Furthermore, when the malaria patients were treated initially with the combination of piperaquine and primaquine, no gametocytaemia has been observed within 20 days.