Although consent must now be obtained before performing any medical treatment, the question of informed consent remains problematic. These problems are accentuated when the patient does not have the capacity to take decisions and it is necessary to obtain consent by representation. This monograph analyses consent by representation from both a health and a legal perspective, with papers from Emilia Civeira, an intensive care specialist, and Jacobo Dopico, lecturer in criminal law. In addition, it contains contributions from professionals in a variety of fields, providing a broad perspective on this topic.