Objective: Even when critically ill patients are almost certain to die from their illnesses, there is generally an element of prognostic uncertainty. Little is known about how physicians handle this uncertainty in conversations with surrogate decision makers. We sought to evaluate whether and how physicians discuss prognostic uncertainty with surrogate decision makers of patients who are highly likely, but not certain, to die. Design: We audiotaped and transcribed discussions between clinicians and surrogate decision makers at two major California teaching hospitals from 2006 through 2008. Physicians completed a questionnaire addressing their prognostic estimates for patients' survival to hospital discharge. Participants: We included physicians and surrogates of 12 incapacitated, critically ill patients. Measurements: We analyzed transcripts of discussions in which physicians' estimates of patients' chances of hospital survival were 1% to 5%; we coded whether physicians disclosed the prognostic uncertainty and, if so, how they conveyed that death was highly likely but not certain. Results: Physicians' estimates of short-term survival were 1% to 5% for 12 of the 70 patients enrolled in the original study. In 8 of 12 cases, physicians conveyed prognostic uncertainty by using probabilistic language or by an explicit mention of uncertainty. In four cases, physicians made at least one statement that either implied or was ambiguous about whether death was certain. Conclusion: We observed variability in how physicians handle prognostic uncertainty in their discussions with surrogates of patients who are highly likely, but not certain, to die, including some circumstances in which physicians stated or implied that death was certain.