The mammalian target of rapamycin (mTOR) is a key signaling node coordinating cell cycle progression and cell growth in response to genetic, epigenetic, and environmental conditions. Pathways involved in mTOR signaling are dysregulated in precancerous human tissues. These findings, together with the intriguing possibility that mTOR suppression may be associated with antitumor actions of caloric restriction, suggest that mTOR signaling may be an important target for chemopreventive drugs.