Physicians are routinely asked to make estimates of patient survival. In providing such estimates, physicians undertake two separate tasks: (1) they formulate a prognosis, or make a mental calculation of the patient's expected survival, and (2) they communicate the prognosis to the inquiring individual, often a patient or the patient's family. The survival estimates, or prognoses, that physicians formulate and then communicate are important to both physicians and patients in all phases of a patient's life because they guide both medical and nonmedical decisions. At the end of life, these prognoses can become critically important, as they may signal a change from primarily curative or life-prolonging care to primarily supportive or palliative care, a change that clearly influences clinical and personal decisions. Ironically, physician prognostication ...