Disposable liquid-crystal temperature-trend indicators were evaluated under clinical conditions that simulated the development of intraoperative hyperthermia during anesthesia. Comparison was made to forehead thermistors for rapidity, accuracy, and linearity of response as well as correlation with esophageal and rectal thermistor recordings. The liquid-crystal monitors were comparable to the forehead thermistors in both rapidity and linearity of response, but not in accuracy. A linear correlation existed with the esophageal thermistor temperatures. Carrelation with the rectal temperatures was not as exact. It is concluded that liquid-crystal thermometers may adequately serve as screening devices for intraoperative hyperthermia.