Legionella pneumophila is a well-recognized etiologic factor in community-acquired pneumonia (CAP). We analyzed the course of radiographic findings of 49 patients with Legionnaires disease, correlated them with clinical and laboratory parameters, and compared them with CAP caused by Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Coxiella burnetii. The most common radiographic finding at admission was unilobar, patchy infiltrate localized in the lower lobes. At follow-up radiography 4 to 12 days after admission, 42.9% of patients developed progression of infiltrates. Mean complete clearing of the infiltrates in most patients (83.7%) was noted on the 21st day of the onset of symptoms. Most patients with Legionnaires disease presented with a clinically mild-to-moderate form, and radiographic findings differed from those seen in other atypical CAPs.