Emergency physicians need to clinically differentiate children with and without radiographic evidence of pneumonia. In this prospective cohort study of 510 patients 2 to 59 months of age presenting with symptoms of lower respiratory tract infection, 100% were evaluated with chest radiography and 44 (8.6%) had pneumonia on chest radiography. With use of multivariate analysis, the adjusted odds ratio (AOR) and 95% confidence intervals (CI) of the clinical findings significantly associated with focal infiltrates were age older than 12 months (AOR 1.4, CI 1.1-1.9), RR 50 or greater (AOR 3.5, CI 1.6-7.5), oxygen saturation 96% or less (AOR 4.6, CI 2.3-9.2), and nasal flaring (AOR 2.2 CI 1.2-4.0) in patients 12 months of age or younger. The combination of age older than 12 months, RR 50 or greater, oxygen saturation 96% or less, and in children under age 12 months, nasal flaring, can be used in determining which young children with lower respiratory tract infection symptoms have radiographic pneumonia.