One-hundred and twenty plant extracts were prepared from 29 Indonesian plants and were primarily tested in vitro cytotoxicity in cultured human lung (A549), colon (Col2), and stomach (SNU-638) cancer cells. As a result, the 23 extracts were found to be active in the criteria of $ED_{50}$<$20;{mu}g/ml$. Remarkable cytotoxicity was observed for chloroform and n-butanol extracts of Calotropis gigantea, with $ED_{50}$ values ranging from 0.25 to $0.46;{mu}g/ml$. Five extracts derived from Eclipta alba and Excoecaria cochinchinensis displayed potent cell-line selective cytotoxicity, while the rest of 15 extracts showed modest cytotoxic activity against all of three cancer cells. In addition, the cytotoxic potential of subfractions of Zingiber cassumunar against a panel of human cancer cell lines is presented.