Abstract: During 1985-1986, a comparative double blind randomized trial was carried out in Hainan Island where Plasmodium falciparum is resistant to chloroquine.Fifty cases of falciparum malaria were treated with l800mg amodiaquine (AQ)/3 days, with 65.3% cure rate fonly 50% cure rate in the migrant cases). 30.7 hr and 60.3 hr were needed to clear their fever and asexual parasitaemia, respectively. 34.7% of all cases showed RI and RII.Twenty-one cases were treated with Fansidar(FD) at a single dose of l 500mg. The fever clearance time was 56.1 hr and asexual parasitaemia clearance time, 61.1 hr. Among 21 cases, 19 cases were cured, l case showed RI, l case showed S-RI. Fansidar was not good in fever control, but rather good in radical cure. Forty-nine cases were treated with amodiaquine plus fansidar (AFD) and 50 cases were treated with amodiaquine plus sulfadoxine (AS). Fever was controlled in 25.7 hr. and 25.0 hr., and the asexual blood parasites were eliminated in 52.8 hr. and 57.1 hr. respectively. Cure rate was 100% and 97.9% respectively.After drug administration, the rate of gametocytemia was rather high in the 4 groups, with the highest positive rate of 95.2% in FD group.