Because these potential benefits have such strong face validity, 24-h in-hospital intensivist staffing has been implemented in many academic institutions, despite the lack of evidence that these benefits actually accrue, and perhaps without full consideration of this policy’s potential downsides. One risk of nocturnal intensivist staffing involves resident autonomy. Experiential learning has unquestionable value in medical training, and the presence of constant supervision by an attending physician could improve the learning experiences of trainees through greater exposure to bedside teaching, immediate feedback to trainees, and real-time refinement of clinical decisions. However, if increased supervision leads to a more passive roles for trainees, fewer opportunities to make decisions, and a reduced sense of personal responsibility for patients’ welfare, greater supervision today could reduce the quality of the physician workforce tomorrow. Will residents exit their training with less confidence and competence without having been empowered to “run the unit” (typically with telephone backup) at night? The current shortage of trained intensivists, insufficient to staff all ICUs even during daytime hours,6 raises a second risk in rapidly implementing 24-h attending physician staffing: that it may exacerbate existing disparities in health-care access, because the more prosperous hospitals attract disproportionate numbers of specialists, leaving increasing numbers of other institutions with inadequate coverage or none at all. Third, as has happened with implementation of resident work hours reforms,7 broad implementation of 24-h intensivist staffing could lead to its acceptance as the standard of care, precluding experimental evaluation of either its intended or unintended effects, thereby sabotaging opportunities to improve on the original model.