Chemical carcinogenesis is associated with the increase of intracellular polyamine levels, and 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse epidermal ODC activity are essential to skin tumor promotion by TPA. Therefore, for the discovery of new cancer chemopreventive agents, we have evaluated about 73 kinds of natural products to study inhibitory effects against ODC activity induced by TPA in T24 cell culture system. The total methanol extracts of plants fractionated into three layers (hexane, ethyl acetate and water layer) were tested and the hexane fraction of Angelica gigas $(root;bark,;IC_{50}:;7.4;{mu}g/ml)$ and the ethyl acetate fraction of Corydalis ternata $(root,;IC_{50}:;7.5;{mu}g/ml)$ were the most effective on the inhibition of TPA-induced ODC activity, These active fractions are under investigation with further sequential fractionation using column chromatography.