Abstract: A new oral dosage regimen and formulation of pyronaridine basing on tne pharma-cokinetic studies and a theoretical dosage regimen reported pnviously, was clinically evaluated for its therapeutic and undesirable effects on falciparum malaria patients in west Hainan Province, where chloroqine-resistant falciparum malaria was prevalent. 32 cases were treated with pyronaridine by tne new dosage regimen of 0.5g in d1 and 0.3g in d2 in plain tablets(groupA), while additional 32 patients received enteric-coated tablets of pyronaridine by the current dosage regimen as a control(groupB), which was 0.4g×2 on dn and 0.4g on d2. The average fever clearance time for A and B groups was 27.0 ± 14.1 and 30.2±13.8h respectively(P0.05),and the clearance time for asex-ual parasites was 57.2±10.2 and 57.9±8.7h. Upon 28d following-up examination, the cure rates were found to be 100% in group A and 93.8% in group B. The undesirable responses were recorded in 18.8% of group A patients(6/32), and 28.1% of group B (9/32)respectively, and they were light and tolerable and short in time duration. It was shown that the new dosage regimen of pyronaridine could retain the same therapeutic effect as that currently used, although the total dose was reduced by one third. Hence, an important basis was provided for more rational use and further study of pyronaridine in malaria therapy.