Physicians have an ethical duty to accurately determine and clearly communicate a patient’s prognosis because a patient’s or surrogate’s decision whether to consent for aggressive treatment rests largely on their understanding of the patient’s diagnosis and prognosis. Pitfalls in determining prognosis include uniformed summary judgement based on faulty pattern recognition, inadequate outcome data, utter reliance on retrospective studies, statistical limitations, nongeneralizability of outcome data, and the fallacy of the self-fulfilling prophecy. Pitfalls in physicians’ communication of prognosis include inadequate time spent in discussion, use of technical jargon, biased framing of decisions, unjustified physician bias, patient innumeracy, ethnicity barriers, and surrogates’ unfounded intuitions about critical illness and death. Improving the recognition of and surmounting the barriers to accurate determination and clear communication of prognosis can make critical care physicians more scientific and virtuous.