Living organ donation requires hurting one person-at least physically-to help another. This can be morally justifiable if certain ethical criteria are met, among them voluntary and informed consent. In the existing guidance, voluntariness is usually vaguely defined as the absence of coercion. This, however, is not enough as a basis for making well-considered decisions in individual cases. A comprehensive evaluation, procedural safeguards, and critical awareness of potential pitfalls can help establish the voluntariness of the donor's decision.