Physicians may employ the concept of medical futility to justify a decision not to pursue certain treatments that may be requested or demanded by patients or surrogates. Medical futility means that the proposed therapy should not be performed because available data show that it will not improve the patient's medical condition. Medical futility remains ethically controversial for several reasons. Some physicians summarily claim a treatment is futile without knowing the relevant outcome data. There is no unanimity regarding the statistical threshold for a treatment to be considered futile. There is often serious disagreement between physicians and families regarding the benefits to the patient of continued treatment. Medical futility has been conceptualized as a power struggle for decisional authority between physicians and patients/surrogates. Medical futility disputes are best avoided by strategies that optimize communication between physicians and surrogates; encourage physicians to provide families with accurate, current, and frequent prognostic estimates; assure that physicians address the emotional needs of the family and try to understand the problem from the family's perspective; and facilitate excellent palliative care through the course of the illness. Critical care physicians should support the drafting of state laws embracing futility considerations and should assist hospital policymakers in drafting hospital futility policies that both provide a fair process to settle disputes and embrace an ethic of care.