The aim of this study was to describe the findings on plain chest radiographs in patients with herpes simplex virus pneumonia (HSVP). The study was based on 17 patients who at a retrospective search have been found to have a monoinfection with herpes simplex virus. The diagnosis was established by isolation of the virus from material obtained during fiberoptic bronchoscopy (FOB) which also included broncho-alveolar lavage and tissue sampling. Fourteen patients had a chest radiograph performed within 24 h of the date of the FOB. Two radiographs showed no abnormalities of the lung parenchyma. The radiographs of the other 12 patients showed lung opacification, predominantly lobar or more extensive and always bilateral. Most patients presented with a mixed airspace and interstitial pattern of opacities, but 11 of 14 showed at least an airspace consolidation. Lobar, segmental, or subsegmental atelectasis was present in 7 patients, and unilateral or bilateral pleural effusion in 8 patients, but only in 1 patient was it a large amount. In contradiction to the literature which reports a high correlation between HSVP and acute respiratory distress syndrome (ARDS), 11 of 14 patients did not meet the pathophysiological criteria for ARDS. The radiologist may suggest the diagnosis of HSVP when bilateral airspace consolidation or mixed opacities appear in a susceptible group of patients who are not thought to have ARDS or pulmonary edema. The definite diagnosis of HSV pneumonia can be established only on the basis of culture of material obtained by broncho-alveolar lavage.