Severe community-acquired pneumonia (CAP) requiring admission to an intensive care unit (ICU) has been inadequately studied. We compared characteristics and outcomes of patients with CAP who were admitted to the ICU with those of patients managed on the ward. Of the 3675 patients hospitalized with CAP, 374 (10%) were admitted to the ICU. The main reason for ICU admission was respiratory failure requiring intubation and ventilation (n = 303, 81%), although this indication decreased with increasing age (p < 0.05 for trend). Most patients (62%) required mechanical ventilation for 3 days or less. The following factors were predictive of ICU admission on multivariable analysis: younger age, smoker, limitation of functional status, absence of cough or pleurisy, presence of chronic obstructive pulmonary disease, substance abuse, elevated serum creatinine, abnormal serum glucose concentration, and a respiratory rate of <16 or >24 breaths per minute. Patients with low Pneumonia Severity Index scores and low CURB-65 scores were admitted to the ICU based on clinical judgment that appeared to supersede objective scoring. Severe CAP requiring admission to the ICU is common, and the decision about which patients to admit often requires clinical judgment that in many cases appears at odds with various validated pneumonia severity scoring systems.