Consent protects the right of patients to decide what happens to them. Before any medical intervention, adults must give valid consent, which must be voluntary, informed and given free of undue influence. When consent is being obtained, patients must be informed about the intervention, why it is being done and its risks; information they are given must be recorded. Every effort should be made to explain the issues in terms that the patient can understand and by providing support and aids to communicate. Consent can be expressed, where patients say they consent or put it in writing, or implied, where a healthcare professional infers from their behaviour that they consent. While different types of consent are valid, some are evidence of stronger proof in court that valid consent has been given. Competent adults have the right to refuse treatment, regardless of the reasons they give for refusal and even if the refusal will result in death; clinicians must respect their decision. In some circumstances-such as when an unconscious person is admitted as an emergency-healthcare professionals can make decisions on behalf of patients, and must do so in patients' best interests.