When engaging in clinical decision making, physicians tend to value primarily information about the effect of treatments on physiological functioning and disease progression, rather than information about the impact on the patient's quality of life. Without having some idea about how the patient values his or her quality of life at present, however, physicians cannot determine what treatment will most benefit the patient. What we view as best for the patient must inevitably include a quality-of-life component because what we call medically indicated treatments presuppose certain values and certain standards of quality of life that may not be true for every patient. Quality-of-life considerations do not only take place in extreme medical situations such as withdrawal of treatment in severely disabled newborns or in patients in a persistent vegetative state, but are part of every treatment consideration for each physician in everyday clinical life. This month's issue explores subtle quality-of-life considerations as well as the philosophical claims about measuring such perceptions and the practical aspects of using quality-of-life rankings when attempting to allocate resources.