An in vitro cytotoxicity screening of the Typhonium flagelliforme extracts indicated high cytotoxicity effect on human lung carcinoma NCI-H23 cells and human mammary gland carcinoma T-47D cells, but the extracts were not active on human liver carcinoma HepG2 cells. NCI-H23 cells were more susceptible to T. flagelliforme extracts than T-47D cells. $EO_{50}$ values of the hexane fractions of the mature plant and the in vitro plantlet of T. flagelliforme on NCI-H23 cells were less than $2{mu}g/mL$. Extract from the mature plant was relatively more cytotoxic than the one from in vitro plantlet except for the hexane fraction. The chloroform and butanol fraction of the mature plant had higher cytotoxicity effect than the fraction from in vitro plantlet on NCI-H23 cells. All the 3 fractions (hexane, chloroform, and butanol) of the mature plant exhibited higher cytotoxicity effects on human mammary gland carcinoma T-47D cells than the 3 fractions of in vitro plantlet. However, the human liver carcinoma cells were resistant to T. flagelliforme extracts except for higher concentration of hexane fractions of both the mature and the in vitro plants and the chloroform fraction of the mature plant. Micropropagated plantlets of T. flagelliforme could hence be used as herbal materials for the treatment of human lung and breast cancers.