This report outlines the structure scheme and development of a new antimalarial drug pyronaridine, which was synthesized from either 2-aminopyridine or pyridine. A series of in vivo and in vitro experimental studies and the assessment of toxicity revealed pyronaridine to be a promising agent against erythrocytic stage of malaria parasites. It exhibited low toxicity and had no cross-resistance to chloroquine. Clinical administration in malaria cases showed high efficacy and mild side-effects. In order to retard the development of resistance of Plasmodium falciparum to pyronaridine, a combination of pyronaridine/sulfadoxine/pyrimethamine was used in the treatment of chloroquine-resistant falciparum malaria in Hainan Province. Further in vivo test was carried out to monitor the sensitivity of P. falciparum to this combined formula for 5 years (1986-1990) in Diaoluo area where chloquine-resistant falciparum malaria was prevalent. Drug resistance was not demonstrated in this field study.