Isorhamnetin from the aerial parts of Persicaria thunbergii has been reported to have anti-tumor activity mediated by the inhibition of farnesyl protein transferase. In this study, we investigated the anti-proliferation effects of isorhamnetin on NIH3T3, K-RAS, H-RAS and SW620 cells, and it showed anti-proliferative effects in a dose-dependent manner with $IC_{50}$ value 4.1, 7.9, 20.2, and $22.4{mu}g/ml$, repectively.