Summary Natural law ethics has much to contribute to an assessment of core values in bioethics. In natural law ethics, reason recognizes intrinsic goods persons seek for human fulfillment. Among these goods are life itself, practical reasonableness, aesthetic experience, play, bodily integrity, friendship, and others; and natural law asserts that there is a structure to moral meaning that presents to reason ‘objective moral principles’ that help in securing these goods. These are common moral agreements that reasonable people of good will can affirm. Despite being described as ‘objective,’ these common moral agreements are not moral absolutes. Reasonable persons of good will affirm them universally, and the work of moral reasoning is to consider how these principles or agreements apply in particular situations. Moral problems arise when some challenge of situation or circumstance suggests that good reason might exist to consider making an exception to a common moral agreement. Just war thinking, which is a product of natural law ethics, is a primary example of how a natural law ethic works—the common moral agreement that force should not ordinarily be used to settle conflicts is accompanied by several justice-related criteria, which, if satisfied, allow an exception to be made for a justified yet constrained use of force. Just war provides a model for how a natural law ethic approaches moral problems, and it is applicable to issues in bioethics. Medical futility illustrates how a natural law ethic works in the bioethics arena. Reasonable people of good will agree that persons facing distressful end-of-life medical conditions should receive care, but futility raises the issue about the extent of that care. The case of Baby K is presented. Baby K was an anencephalitic baby born without a cerebral cortex. Her situation was medically catastrophic, and she had no reasonable prospect of flourishing, that is, of enjoying the goods of life. The good of life itself had no value to her. Baby K's mother, however, because of sanctity of life commitments, requested aggressive care, including surgeries, which medical staff did not want to perform given the baby's futile medical condition. The courts, following an American federal law that requires hospitals to provide emergency care to any patient, sided with the mother, and the baby received aggressive treatment, living longer than babies with this condition usually do. The case raises bioethics issues related to futility. Baby K received treatment because reasonable people of good will universally agree that even severely distressed patients should receive medical care. On the natural law ‘just war’ model, however, given Baby K's dire situation, several criteria can be advanced that, if satisfied, would allow for a justified withdrawal or withholding of treatment in favor of palliation. Those criteria deal with such things as physician determinations that therapeutic interventions can no longer provide a patient any benefit, clear communications with families and surrogate decision-makers about medical prognosis, and attention to gender or racial bias that might affect the delivery of care and decisions about futility. The emphasis of the natural law approach is on reasoned deliberation as medical professionals address issues identified in the criteria of ‘just futility’ and consider the next steps in patient care. Values related to goods of life emerge from deliberating futility concerns. The patient as person and the life of the patient are clearly core values as is practical reasonableness, which, as a good of life, comes into conflict with the good of life itself in futility cases. Natural law ethics moves toward decision-making by means of rational and informed deliberations over ethical matters, and it values as well equity and equality of persons, open communications, and approaching death as a natural part of the life process. Attention is given to patient-centered care, dialogue and clear communications between medical staff and families, as well as to the possibility that beneficence may overrule autonomy should families resist the justified withholding of aggressive care. Core values related to futility and to patient care, in general, can be identified in this discussion of a natural law approach to bioethics.