For thousands of years, plants show great importance in applications such as condiments, medicines, fragrances, colorants, ornaments, and thus through time scientific information has been obtained for botany, horticulture, chemistry and pharmacology. It is estimated that more than one billion dollars is spent in the commerce of medicinal plants and spices, and its study has greatly contributed to understand the physiological processes of photosynthesis and ecological relation of plants with the environment. Furthermore, plants continue to provide significant roles in traditional rituals of different societies. Presently, scientific research done by several institutions on natural products, have greatly contributed to the search for potential food and pharmacological products, and has greatly increased the interest of industry in the study of the methodology to explore the ecological, botanical, tissue culture, chemistry and pharmacological relation between plants, thus creating a great demand for professionals and specialists associated with botany, chemistry and pharmacology. For this reason, there is demand for more information about this knowledge, but there exists little scientific information that can provide a deep review of research in medicinal plants. This book presents 1752 compounds isolated and identified from plants that present anticancer activity. These substances have been classified by chemical groups and each provides the most relevant information of its pharmacological activity, action mechanism, chemical structure and other properties.