To determine how well triage temperature and pulse abnormalities in elderly patients with potential infections predict antibiotic administration and hospital admission. Data from the National Hospital Ambulatory Care Survey (2001-2002), a sample of US emergency departments, were used. Patients (>or=65 years) with a reason for visit suggesting potential infection were included. Of 10,586 patients 65 years or older, 32% had reasons for visit suggesting potential infection. The negative predictive value for predicting intensive care unit admission (n = 154) for triage hyperthermia (temperature >or=38 degrees C) was 96% (95% confidence interval, 95%-96%); hypothermia (temperature <or=36 degrees C), 95% (95%-96%); pulse higher than 90, 97% (96%-98%); both pulse higher than 90 and hypothermia or hyperthermia, 96% (95%-96%); and either pulse higher than 90 or hypothermia or hyperthermia, 96% (95%-97%). The negative predictive value for the combined outcome of hospital admission and antibiotic administration (n = 432) for hyperthermia was 90% (88%-91%); hypothermia, 87% (86%-88%); pulse higher than 90, 90% (89%-92%); for both pulse higher than 90 and hypothermia or hyperthermia, 89% (88%-90%); and for either pulse higher than 90 or hypothermia or hyperthermia, 91% (90%-93%). Although the absence of pulse and temperature abnormalities in elderly patients with potential infection is predictive of not being admitted to the intensive care unit and the combined outcome of admission and hospitalization, this information should not be used alone to determine the presence or absence of a potentially time-sensitive infection.