Andrographis paniculata Nees. which is known in Indonesia as ‘sambiloto’ is used as antimalarial drug. Andrographolide is the main content of sambiloto which is believed to have antimalarial activity. The previous researches show that sambiloto extract have the antimalarial activity both in vitro and in vivo. But, there is no data for the effective dose of standardized sambiloto extract as antimalaria. In this research, the standardized extract of sambiloto was tested in vivo as antimalarial agent using Peter’s 4 day suppressive test. Mice (16-29 body weight) were infected with Plasmodium berghei intra peritoneally with suspension containing infected red blood cell taken from donor mice with parasitemia >20%, when parasite concentration in erythrocyte reached >1%, treatment with suspension extract was given for four consecutive days orally with doses 0.0005-100 mg andrographolide/kg body weight. Blood samples were taken to determine parasitemia level for seven days and compared to non treated and chloroquin treated subjects and ED50 was obtained by analyzing inhibition level in five days with probit analysis. The result showed that ED50 of standardized sambiloto extract (containing 10.82±0.37 % andrographolide) against Plasmodium berghei was 12.2223 mg extract which was equal to 1.3200 mg andrographolide/kg body weight. Key words: Andrographis paniculata, Andrographolide, Antimalarial, Plasmodium berghei