Iatrogenic illnesses are those that arise as a result of the process of medical care and are potentially preventable by improvements to patient care. The term is commonly used to denote medical error; however, for the critically ill patient the term has a much more fundamental meaning. Critical illness is inherently iatrogenic: it only develops in those patients who have been resuscitated from an otherwise life-threatening disorder, and its subsequent evolution is shaped by the beneficial and adverse consequences of therapeutic and supportive interventions. The construct of organ dysfunction describes both the nature of this support and its inadvertent consequences. This review explores evolving evidence on the iatrogenic nature of critical illness and the implications of an iatrogenic model of disease on the taxonomy, management, and prevention of the complex processes that threaten to limit the survival of the critically ill patient.