Objective: To develop practice parameters for the evaluation of adult patients who develop a new fever in the intensive care unit (ICU) for the purpose of guiding clinical practice. Participants: A task force of 13 experts in disciplines related to critical care medicine, infectious diseases, and surgery was convened from the membership of the Society of Critical Care Medicine, and the Infectious Disease Society of America. Evidence: The task force members provided the personal experience and determined the published literature (MEDLINE articles, textbooks, etc.) from which consensus would be sought. Published literature was reviewed and classified into one of four categories, according to study design and scientific value. Consensus Process: The task force met several times in person and twice monthly by teleconference over a 1-yr period of time to identify the pertinent literature and arrive at consensus recommendations. Consideration was given to the relationship between the weight of scientific evidence and the experts’ opinions. Draft documents were composed and debated by the task force until consensus was reached by nominal group process. Conclusions: The panel concluded that, because fever can have many infectious and noninfectious etiologies, a new fever in a patient in the ICU should trigger a careful clinical assessment rather than automatic orders for laboratory and radiologic tests. A cost-conscious approach to obtaining cultures and imaging studies should be undertaken if it is indicated after a clinical evaluation. The goal of such an approach is to determine, in a directed manner, whether or not infection is present, so additional testing can be avoided and therapeutic options can be made. (Crit Care Med 1998; 26:392-408) In some intensive care units (ICUs), the measurement of a newly elevated temperature triggers an automatic order set which includes many tests that are time consuming, costly, and disruptive (Table 1). Moreover, the patient may experience discomfort, be exposed to unneeded radiation, or experience considerable blood loss due to this testing, which is often repeated several times within 24 hrs, and daily thereafter. In an era when utilization of hospital and patient resources is under intensive scrutiny, it is appropriate to assess how such fevers should be evaluated in a prudent and cost-effective manner. The American College of Critical Care Medicine of the Society of Critical Care Medicine and the Infectious Disease Society of America established a Task Force to provide practice parameters for the evaluation of a new fever in patients in an ICU with the goal of promoting the rational consumption of resources and promoting an efficient evaluation. These practice parameters presume that any unexplained temperature elevation merits a clinical assessment by a healthcare professional that includes a review of the patient's history and a focused physical examination before any laboratory tests or imaging procedures are ordered. These practice parameters specifically address how to evaluate a new fever in an adult patient already in the ICU who has previously been afebrile and in whom the source of fever is not initially obvious. If the initial evaluation of history and physical examination reveals a consolidated lung, a purulent wound, or a phlebitic leg, then diagnosis and therapy of that infectious process should commence: such management is addressed by other practice parameters aimed specifically at pneumonia, catheter-related infections, etc. Specific questions addressed in these practice parameters relate to the search for the underlying cause of fever and include: a) What temperature should elicit an evaluation? b) When are blood cultures warranted? c) When should intravascular catheters be cultured or removed? d) When are cultures of respiratory secretions, urine, stool, or cerebral spinal fluid warranted? e) When are radiographic studies warranted? These practice parameters do not address children, since children have different issues that merit discussion in a separate document. In addition, these practice parameters do not address an approach to persistent fever after the initial evaluation, or to localized infection once the anatomic source of fever has been identified. These issues are addressed in other monographs or practice parameters. The current document also does not address the desirability or selection of empiric vs. specific therapy since the need for therapy is so dependent on clinical evaluation and the underlying disease. It did not appear to this task force that useful therapeutic guidelines could easily be provided which took into account the acuity of illness, the underlying disease process, concurrent drugs (i.e., immunosuppressive agents, and antimicrobials), ability to tolerate toxicities, and geographic antibiotic susceptibility differences. Each ICU must establish its own policies for evaluating fever that take into account the type of ICU involved (e.g., medical ICU, surgical ICU, burn ICU, etc.), the specific patient population (e.g., immunosuppressed vs. immunocompetent, elderly vs. younger adults), recent epidemics (e.g., out-breaks of Clostridium difficile diarrhea or vancomycin-resistant Enterococcus), or endemic pathogens (e.g., methicillin-resistant Staphylococcus aureus). It is hoped that these practice parameters will assist intensivists and consultants as a starting point for developing an effective and cost conscious approach appropriate for their patient populations. The specific recommendations are rated by the strength of evidence, using the published criteria of the Society of Critical Care Medicine (Table 2).