Ethanol extracts from Xanthii Fructus (XFE) and Prunellae Spica (PSE) were investigated for the effects on the induction of cancer chemoprevention-associated enzymes. The following effects were measured: (a) induction of quinone reductase (QR) (b) induction of glutathione S-transferase (GST) (c) reduced glutathione (GSH) level. XFE and PSE were potent inducers of quinone reductase activity in Hepa1c1c7 murine hepatoma cells. Glutathione levels were increased with XFE and PSE. In addition, glutathione S-transferase activity was increased with XFE. However, GST activity was not increased with PSE. These results suggest that XFE and PSE have chemopreventive potentials by inducing quinone reductase and increasing GSH levels.