Abstract: Suppressive effect of piperaquine + nitroquine, hydroxypiperaquine + nitroquine and pyronaridine + nitroquine combinations in rhesus monkeys infected with Plasmo-dium cynomolgi were observed. The results suggested that piperaquine 3.5 mg/kg·d×7 + nitroquine 0.1 mg/kg·d×7, hydroxypiperaquine 3.5 mg/kg·d×7 + nitroquine 0.1 mg/kg·d×7 and pyronaridine 5 mg/kg·d×7 + nitroquine 0.1 mg/kg·d×7 can all cure the monkeys infected with P.cynomolgi. Until D105 after administration, recrudescence of parasitaemia did not occur in any of the test monkeys. By contrast, after piperaquine 3.5 mg/kg·d×7,hydroxypiperaquine 3.5 mg/kg·d×7, pyronaridine 5mg/kg·d×7 or 10mg/kg·d ×7 and nitroquine ×0.1 mg/kg·d×7 or 0.15×7 were administratered respectively, para-sitaemia in all of the test monkeys reappeared within one month.