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Introduction The clinical and epidemiological significance of community-acquired pneumonia (CAP) with a chest radiograph demonstrating no parenchymal infiltrate has not been studied. We determined the percentage of patients with a clinical diagnosis of CAP who did not have radiographic opacifications and compared this group with patients with CAP and radiographic infiltrates. Methods Patients admitted with a diagnosis of CAP were identified. Clinical history, physical examination, laboratory studies, and microbiological cultures were reviewed in a random sample of 105 patients. Admission and subsequent chest radiographs were interpreted without knowledge of the clinical data. Results Twenty-one percent (22/105) of patients with a clinical diagnosis of CAP had negative chest radiographs at presentation. Demographic, clinical, and laboratory data were the same in both groups. Fifty-five percent of patients with initially negative chest radiographs who had follow-up studies developed an infiltrate within 48 hours. Conclusions In patients admitted with a clinical diagnosis of CAP, the initial chest radiograph lacks sensitivity and may not demonstrate parenchymal opacifications in 21% of patients. Moreover, greater than half of patients admitted with a negative chest radiograph will develop radiographic infiltrates within 48 hours. Further studies are needed to develop evidence-based criteria for the diagnosis of CAP.