‘Consent’ outlines the generally recognized principles of the law of consent. It considers what is a competent adult and shows that once can demand omissions (refuse treatment), but not demand acts (insist on specific treatment). In the cases of incompetent adults and children, how one decides how to make a decision on someone else's behalf, and who does it, is discussed. The issues of when consent is not consent and ‘informed consent’ are then explained. Finally the criminal, civil, and disciplinary consequences of failing to obtain the patient's consent are discussed.