Chemoprevention, a relatively new and promising strategy to prevent cancer, is defined as the use of natural dietary compounds and/or synthetic substances to block, inhibit, reverse, or retard the process of carcinogenesis. The chemopreventive effects elicited by these natural dietary compounds are believed to include antioxidative, anti-inflammatory activity, induction of phase II enzymes, apoptosis, and cell cycle arrest. Many mechanisms have been shown to account for the anticarcinogenic actions of natural dietary compounds; attention has recently been focused on intracellular-signaling cascades as common molecular targets for various chemopreventive natural dietary compounds. This book presents some theoretical issues, reviews, and a variety of concept of regarding basic cancer chemoprevention in different arena of cancer science.