OBJECTIVES: Hospitalization of patients with CABP places a major burden on the US healthcare system. There are increasing efforts to reduce length of hospital stay (LOS) among pneumonia patients. This study attempts to identify CABP patients at increased risk for prolonged LOS. METHODS: A retrospective study of hospitalized patients with CABP in the Geisinger IDN medical encounter 2010-2015 database was performed. Inclusion criteria: (1) age ≥ 18 years, (2) primary diagnosis for CABP, (3) >1-year enrollment before index CABP hospitalization, (4) received ceftriaxone + macrolide or a fluoroquinolone on hospitalization day 1 or 2 and continued for ≥ 2 days. The primary outcome was LOS ≥ 8 days. RESULTS: During the study period, 1,089 patients met study criteria. The mean (SD) age was 66.7 (16) years. The geometric mean (SD) and median LOS were 4.1 (1.8) and 4.0 days, respectively. Of the 1,089 patients, 171 (15.7%) had LOS ≥ 8 days. LOS ≥ 8 days was similar between the following groups: age ≥ 65 vs. < 65 years (14.4% vs. 16.4%), body mass index ≥ 30 vs. < 30 (12.6% vs. 17.4%), presence of COPD/bronchitis vs. absence of COPD/bronchitis (16.1% vs. 12.8%), CCI ≥ 2 vs. 0-1 (16.2% vs. 14.3%), and previous (non-CABP) hospitalization vs. no previous hospitalization (15.7% vs. 15.8%). Patients with a CURB-65 score ≥ 3 had a statistically significantly higher risk of prolonged LOS ≥ 8 days vs. those with CURB-65 score ≤ 2 (19% vs. 14%, p<0.0001). Patients with LOS ≥ 8 days had a modest elevated risk of 30-day readmissions/repeated ED visits. CONCLUSIONS: Patient populations with CABP thought to be at an increased risk for unfavorable health outcomes were not found to be at an increased risk for prolonged LOS. These findings highlight the need to better delineate patient populations at greatest risk for prolonged LOS.