Abstract: 37 patients in Qionglai County, Sichuan Province suffered from acute vivax malaria were treated with pyronaridine phosphate. A total of 1.2 g (base) was administered in 4 divided doses i.e. 0.3 g initially, repeatedly 6-8 hours later and once daily in the following 2 days. Twenty acute vivax malaria patients in the same district were treated with chloroquine phosphate in similar dose schedule as control.All the patients treated with pyronaridine phosphate became free from parasite in an average of 59.3 hours and free from fever in 25.5 hours, while patients treated with chloroquine in 60 hrs and 28.1 hrs. Two patients treated with pyronaridine phosphate and one patient with chloroquine had relapse of parasitaemia 30 days later.No significant side-effects were observed in both groups.