Derivatives of steviol, isosteviol and betulinic acid were prepared and tested in vitro against Plasmodium falciparum W2 (chloroquine-resistant) and Trypanosoma cruzi. The best results against P. falciparum were found for the betulinic acid derivatives 3-[(2,4-dinitrophenyl)hydrazono]lup- 20(29)-en-28-oic acid and 3-hydroxy-20-[(2,4-dinitrophenyl)hydrazono]-29-norlupan-28-oic acid (values concentration in that the growth of the parasites is 50% inhibited, IC50 = 9.96, 6.45 and 21.06 µg mL-1, respectively). Isosteviol was inactive but its 4-nitro- and 2,4-dinitrophenylhydrazone showed moderate activity (IC50 = 17.50-22.58 µg mL-1). The derivatives of betulinic acid were more selective to the parasite when compared with hepatoblastoma HepG2 A16 cells. The results showed that nitrophenylhydrazone derivatives of lupane and beyerane terpenes are promising prototypes of antimalarial agents. Among the compounds tested against T. cruzi the oxime of isosteviol was active against both epimastigote and trypomastigote forms of the parasite.