Objective: The efforts to obtain new antimalarial medicine were among others to explore and to develop both natural substances and synthetic compounds whose activities have been established. An in vitro antiplasmodial activity test was carried out to several plants from Borneo to find out IC50 Methods: Dried materials of H. spinosa leaves, A. rubiginosa tubers, U. crinita roots and A. avecta tubers were extracted using 96% ethanol with maceration method. An in vitro antiplasmodial activity test was carried out to the resulting ethanol extracts of the four plants using candle jar method. The resulting data were processed using probit analysis to give the IC value in the effort to explore new antimalarial plants. 50 Results: The results of the study included parasitemia percentage, P. falciparum growth inhibition percentage and IC value. 50 value. At low concentration (1 μg/ml) of the four tested materials gave the parasitemia percentage of H. spinosa, A. rubiginosa, U. crinita and A. evecta of 10.89±1.29%, 10.58±0.67%, 11.20±0.86%and 8.32±2.44 %, respectively. Meanwhile, P. falciparum growth inhibition percentage were 34.68±8.13%, 33.64±4.23%, 11.83±3.42%and 47.83±3.24 %, respectively. And, the biggest P. falciparum percentage of the four plants was 47.83±3.24% that took place toA. evecta. The IC50 Conclusion: The in vitro antiplasmodial activity of the four ethanol extracts indicated that the H. spinosa leaves were classified to be inactive, the A. rubiginosa tubers and the U. crinita tubers were active and the A. evecta tubers were very active. values of the ethanol extract of theH. spinosa, the A. rubiginosa, the U. crinita and the A. evectawere more than 250, 9.38±8.26, 25.48±3.10, and 2.86±0.27μg/ml, respectively