Excessive alcohol consumption and smoking are among the major risk factors for cancer. Simultaneous indulgence further increases the risk for especially cancer of the upper aerodigestive tract due to the interaction of several metabolic and genetic factors. The first part of this book addresses in detail the correlations between alcohol and carcinogenicity, focusing on specific organs such as the upper aerodigestive tract, liver, colon, pancreas and breast. This includes the impairment of methionine-folate metabolism and DNA methylation by alcohol, as well as the use of s-adenosylmethionine to prevent cancer. Furthermore, the synergistic effects of reactive oxygen species and iron in producing liver cancer are addressed. The second part is dedicated to the role of tobacco in lung and digestive tract cancers and to their prevention, highlighting the role of phytochemicals. More specifically, the mutagenic, mitogenic, precarcinogenic, anti-apoptotic, and immunosuppressive properties of nicotine which are involved in the development of cancer, and the possible use of nicotine vaccine in the prevention of mortality associated with tobacco, are discussed. Highlighting general mechanisms leading to cancer and providing the latest information on the underlying mechanisms whereby alcohol consumption and tobacco use initiate and/or promote carcinogenesis, this book is a valuable source of information for all those interested in the topic.