To test whether there is a radiographic pattern diagnostic for chronic eosinophilic pneumonia (CEP), radiographs of 591 patients with interstitial lung disease (2,852 films) were reviewed. A peripheral ground glass pattern was seen in 24 individuals (4.1%). Lung biopsies in 16 of these patients revealed CEP. The remaining eight bad all the clinical features of CEP. In a separate study, pathologic featues of 350 patients with interstitial disease were coded: CEP was the principal diagnosis in 21 (5.7%). Sixteen of the 21 had typical peripheral radiographic opacities. Review of published chest radiographs of 81 patients with CEP showed characteristic peripheral opacities in 53 cases (65%). Typically, dense opacities with ill-defined margins and without lobar or segmental distribution are seen arranged peripherally apposed to the pleura. The opacities are usually in an apical or axillary location, but are sometimes basal when they mimic loculated effusion. When the opacities surround the lung, the appearance is that of a photographic negative or reversal of the shadows usually seen in pulmonary edema. The opacities sometimes disappear and recur in exactly the same locations. Peculiar oblique or vertical lines without reference to hilus or anatomic divisions occasionally appear during resolution. Response to corticosteroid treatment is dramatic, with clinical improvement in hours and disappearance of radiographic shadows within a few days. The typical radiographic pattern is virtually diagnostic even without other information. In this series all patients with characteristic radiographs had CEP. Blood eosinophilia is confirmatory, but its absence does not exclude the diagnosis.