PURPOSE Tissue oxygen saturation (StO2) is a noninvasive measure that reflects changes in tissue perfusion. Rapid response teams (RRTs) assess sick inpatients to determine need for intensive care unit (ICU) admission. This determination is subjective based on parameters such as systolic blood pressure, heart rate, and pulse oximetry. Our objective was to determine if parameters readily available at RRT bedside assessment (vital signs and StO2) can predict ICU admission and inhospital mortality. MATERIALS AND METHODS All inpatients assessed by RRT at a tertiary Canadian hospital were consecutively sampled for 3 months. After clinical assessment, the RRT physician (blinded to StO2) made the ultimate ICU admission decision. RESULTS In 134 included patients, mean age was 65.5 ± 15.2 years, and 53% (n = 71) were males. There were 49 ICU admissions (36.6%) and 31 mortalities (23.1%). Two multivariable models significantly predicted ICU admission and inhospital mortality. The only independent predictor of ICU admission was pulse oximetry (adjusted odds ratio, 0.88; 95% confidence interval, 0.80-0.96; P = .007). Tissue oxygen saturation did not predict ICU admission but was the only independent predictor of mortality (adjusted odds ratio, 1.06; 95% confidence interval, 1.01-1.12; P = .04). CONCLUSIONS Tissue oxygen saturation may identify critical illness in patients who would not traditionally meet ICU admission criteria and thus may identify patients who benefit from closer monitoring.