One-hundred and twenty plant extracts were prepared from 29 cIndonesian 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 ED50<20 μg/ml. Remarkable cytotoxicity was observed for chloroform and n-butanol extracts of Calotropis gigantea, with ED50 values ranging from 0.25 to 0.46 μg/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.