Background Sepsis risk stratification tools typically predict mortality, although stays in the intensive care unit (ICU) of 24 hours or longer may be more clinically relevant for emergency department disposition. Objective To explore predictors of ICU stay of 24 hours or longer among infected, hypotensive emergency department patients. Methods A secondary analysis of 2 prospective, observational studies of adult patients with severe sepsis or an infection with a systolic blood pressure less than 90 mm Hg in 3 urban, academic emergency departments was performed. Patients with hypotension and infection were included. Patients with emergency department intubation, vasopressor administration, and/or death were excluded. The primary outcome was ICU stay of 24 hours or longer or death in less than 24 hours. Multivariable logistic regression was used to predict ICU stay of 24 hours or longer. Results Of 233 patients, 108 (46.4%) had ICU stays of 24 hours or longer. History of heart failure (odds ratio, 3.6; 95% CI, 1.5-8.3), bicarbonate level less than 20 mEq/L (odds ratio, 2.0; 95% CI, 1.1-3.8), respiratory rate greater than 20/min (odds ratio, 2.0; 95% CI, 1.1-3.7), and creatinine level greater than 2.0 mg/dL (odds ratio, 3.6; 95% CI, 1.9-6.7) were independent predictors of ICU stay of 24 hours or longer (area under curve, 0.74). The presence of 1 of these factors predicted ICU stay of 24 hours or longer (area under curve, 0.74) with 82.4% sensitivity and 49.6% specificity. Conclusions These exploratory results show that heart failure, bicarbonate level of less than 20 mEq/L, tachypnea, or creatinine level greater than 2.0 mg/dL increases the likelihood of an ICU stay of 24 hours or longer among infected, hypotensive emergency department patients.