Abstract: This paper reports the results of the experimental studies on antimalarial effect of hydroxypiperaquine against rodent malaria (Plasimodium berghei). The results obtained showed that the PD₅₀ of hydroxypiperaquine and its phosphate was much larger than that of piperaquine. The CD₅₀ and the resistance index of hydroxypiperaquine and it 7 salts were listed. In comparisons of the therapeutic activities of hydroxypiperaquine, piperaquine and chloroquine at the peak parasitaemia, the former 2 drugs showed almost the same effect, whereas chloroquine was less effective in terms of survival rate of the treated mice and the infection rate of erythrocytes.