Six years ago, we proposed a patient benefit-centered definition of medical futility that included both quantitative and qualitative components. We distinguished between an effect of a treatment that is limited to some part of a patient's body and a benefit that improves the patient as a whole. The quantitative portion of our definition stipulated that physicians should regard a treatment as futile if empirical data show that the treatment has less than a 1 in 100 chance of benefiting the patient. The qualitative portion of our definition stipulated that if a treatment merely preserves permanent unconsciousness or cannot end dependence on intensive medical care, physicians should consider the treatment futile. In this paper, we clarify and modify our original proposal and respond to the following major criticisms: 1) Medical futility is simply an attempt to increase the power of the physician over the patient and to repeal recent hard-gained advances in patient autonomy; 2) no professional or societal consensus has been achieved about the definition of futility; 3) futility is a value-laden determination, the usurpation of which by medicine is inappropriate unless only a so-called value-free or strict physiologic definition of futility is used; 4) the concept of futility is not practically useful because empirical treatment data cannot be applied with certainty to any given patient; 5) futility undermines our pluralistic society and threatens, among other things, the free exercise of religion; and 6) because cost considerations will ultimately dictate all such decisions, futility is an unnecessary concept.