Cancer is a disease defined by a clinico-pathological natural history characterised by uncontrolled growth of a tissue with the ability to spread to other organs. There is no single cause for cancer -we know many factors that increase the risk of cancer at various sites of the body, which we call causes. Their nature is heterogeneous: there are chemicals (e.g. asbestos), viruses (e.g. human papilloma viruses), but also conditions such as being overweight, or being a woman with no children. This book reviews known causes of cancer and quantifies the proportion of the cancer burden in Europe that they explain. The quantities presented measure the changes in the occurrence of the disease that we would expect following the removal of those causes; in other words, the potential impact of primary prevention. Numbers of cases and deaths are attributed to broad categories of causal factors for use in public health planning. With the work presented the authors aim to providing a source of objective and quantitative information to help public health planners, administrators, service providers as well as the general public in their actions to prevent cancer.