Linoleic acid(LA) was examined to evaluate its potential as a chemotherapeutic agent for MG-63 human osteosarcoma and AZ-521 gastric cancer cells. The treatment of LA(0.005% for 6 days) to the MG-63 and AZ-521 cancer cells inhibited growth of the cancer cells by 54% and 52%, respectively as compared to that of the controls. It also exhibited that LA with 0.01% concentration decreased the [$^3$H] thymidine incorporation by more than 90% in the both cancer cells. In additions we observed morphological changes in MG-63 and AZ-521 cells under inverted microscope, and the changes in membrane fatty acid compositions of the cancer cells when LA was added at the level of 0.005%. The treatment with LA revealed that the contents of 16:0 and 18:0 decreased significantly, but fatty acids that C numbers are more than 20 and unsaturated(20:4, 22:6, and 24:4) increased, concomitantly the morphological changes of the cells were observed.