In the context of consent, "voluntariness" refers to a patient's right to make health care choices free of any undue influence. However, a patient's freedom to make choices can be compromised by internal factors such as pain and by external factors such as force, coercion and manipulation. In exceptional circumstances--for example, involuntary admission to hospital--patients may be denied their freedom of choice; in such circumstances the least restrictive means possible of managing the patient should always be preferred. Clinicians can minimize the impact of controlling factors on patients' decisions by promoting awareness of available choices, inviting questions and ensuring that decisions are based on an adequate, unbiased disclosure of the relevant information.