Pneumonia is often diagnosed and treated empirically. We set out to determine the diagnostic accuracy of clinical judgment based on signs and symptoms to detect radiographic pneumonia in patients presenting with acute cough in primary care. In 2810 European patients with acute cough, general practitioners (GPs) recorded whether they considered pneumonia to be present ("yes" or "no") immediately after history and physical examination. Chest radiography was performed within 1 week by local radiologists blind to other patient characteristics. 140 patients had radiographic pneumonia (5%), of whom 41 (29%) had been diagnosed as such. 31 (1%) patients had a clinical diagnosis that was not confirmed by radiography (n=2670). In clinically suspected pneumonia, 57% of subjects were subsequently diagnosed with radiographic pneumonia. Negative predictive value (NPV), sensitivity and specificity of GPs' clinical judgment were 96%, 29% and 99%, respectively. Compared to patients with a clinical diagnosis of pneumonia, less severe symptoms were found in radiographic pneumonia cases not suspected clinically (p<0.05). The predictive values of GPs' clinical judgment, particularly the high NPVs, are helpful in routine care. Nonetheless, the majority of diagnoses of radiographic pneumonias was not suspected on clinical grounds. There is a need to further support the detection of clinically relevant pneumonia in primary care.