The present study used a meta-analysis to examine 4 questions about intraoperative hypothermia. The questions addressed were as follows: (1) Is the difference in adverse patient outcomes between normothermic and mildly hypothermic patient groups significant across studies and within studies? (2) What is the magnitude of the difference in adverse patient outcomes across studies? (3) What are the costs resulting from the difference in adverse patient outcomes? (4) Does a significant difference exist in effectiveness of modality for maintaining intraoperative normothermia? The results of this meta-analytic study provide evidence that the difference in adverse patient outcomes between the normothermic and mildly hypothermic patients is significant across studies for all adverse outcomes examined. The magnitude of this difference and the costs resulting from these adverse outcomes are presented. In addition, a significant difference in effectiveness between warming modalities for maintaining intraoperative normothermia was found. A significant increase in the risk of costly complications occurred when patient temperatures dropped a mean of 1.5 degrees C. For example, patients who become mildly hypothermic are much more likely to receive blood transfusions and to develop infections; both of these outcomes result in increased costs. Minimizing adverse outcomes is critical to cost-effective patient care in today's competitive healthcare environment. The cost of preventing intraoperative hypothermia is much less than the cost of treating the adverse outcomes that affect patients experiencing intraoperative hypothermia. Meta-analytic results allowed us to conclude that hypothermia averaging only 1.5 degrees C less than normal resulted in cumulative adverse outcomes adding between $2,500 and $7,000 per surgical patient to hospitalization costs across a variety of surgical procedures. In conclusion, patients whose temperatures have been maintained at normal levels during the intraoperative period experience fewer adverse outcomes, and their overall hospital costs are lower. Intraoperative normothermia is maintained more effectively with the use of forced air warming.