Individual clinical and laboratory abnormalities are associated with only moderate increases in the odds of death. Thus, combinations of factors are necessary to accurately assess short-term risk for death and guide site-of-care decisions. Moreover, studies of individual factors do not measure the independent association of each factor with mortality risk. In updating a recent review on the prognosis of patients with pneumonia (90), we identified 16 studies that used multivariate analyses to identify independent predictors of poor prognosis for patients with community-acquired pneumonia (67, 72, 74, 84–85, 91–101). These prognosis rules include demographic factors (primarily age), comorbid conditions (for example, neoplastic disease, pulmonary disease, and heart disease), symptoms and signs (for example, altered mental status, lack of pleuritic chest pain, tachypnea, and hypotension), and laboratory and radiographic findings (for example, hypoxemia, azotemia, and multilobar infiltrates). We have included the prognostic scoring of one of these rules, the Pneumonia Patient Outcomes Research Team (PORT) Severity Index (Figure 2)(97) because it meets the most methodologic criteria for prediction rules (90) and was recently demonstrated to perform accurately and effectively in two prospective trials designed to reduce hospitalization of low-risk patients with community-acquired pneumonia (102–103). In one emergency department–based study, patients with scores in risk classes I, II, and III (Figure 2) were recommended for outpatient care. Compared to a historical control period, the rate of hospitalization was statistically significantly reduced during the intervention period without a statistically significant increase in adverse clinical events (although readmission rates were increased) (102). However, several groups of patients were automatically excluded from home triage regardless of their calculated risk class, including patients with chronic oxygen dependency, severe social or psychiatric problems compromising home care, and inability to take oral medications and nutrition. In another study using the same risk class criteria for hospitalization, admission rates were similarly decreased at intervention sites without any increase in adverse event rates compared to standard care sites (103). Of note, in both studies, between 31% and 43% of patients in the lowest risk classes were still hospitalized on the basis of the treating physicians' judgments that the patients were too unstable for home-based care.