All participants must provide a valid consent to surgical clinical trials. A valid consent requires patient capacity, adequate disclosure of information, and voluntariness. Capacity is the ability to understand information relevant to making a decision and to appreciate the reasonably foreseeable consequences of a decision or lack of decision. To protect vulnerable persons, an incapable person should not be enrolled in most clinical trials. The only exception is if the study can only be conducted on incapable persons. If the willing research participant is incapable, consent must be obtained from others through a process called substitute (or proxy) consent. Disclosure refers to the provision of relevant information to the patient and its comprehension by the patient. Most surgical trials carry more than minimal risks, so the requirement for careful disclosure of these risks to potential participants is generally stringent. Voluntariness refers to the freedom of a person to make a treatment decision. In specific circumstances related to emergency research, the requirement for consent may be waived. Waiver can be justified only if the delay required to obtain consent would prevent the research from occurring and only after prior consultation with from the "community" of potential research participants.