Awoman presented as an urgent referral to the interstitial lung disease clinic with dyspnea and a cutaneous rash of several weeks’ duration. Skin biopsy revealed a hypersensitivity vasculitis and chest radiograph revealed multiple pulmonary nodules, many of which were found to contain central cavitation on computed tomography (CT) scan. On basilar slices (Figure 1A), a set of “atoll signs” (Figure 1B) appeared to spell the word “COP,” suggesting the diagnosis. Lung biopsy demonstrated eosinophilic pneumonia with nonnecrotizing vasculitis, but without evidence for granulomas or organizing pneumonia (Figures 1C–1F). The patient responded dramatically to prednisone, but after tapering developed cardiomyopathy and renal infarcts, which were consistent with generalized eosinophilic vasculitis with Churg-Strauss–like features. She is currently stable on Cytoxan and mycophenolate mofetil. The atoll sign, also known as the “reverse halo sign” or “fairy ring” sign, refers to a crescentic or ring-shaped opacity surrounding an area of ground-glass opacification (1). It derives its name from the aerial appearance of an atoll, a coral island partially or completely surrounding a central lagoon (Figure 1B). The atoll sign was first described in patients with cryptogenic organizing pneumonia (2, 3) and was originally believed to be specific for that diagnosis (4). However, this CT appearance has since been reported in a large number of pulmonary disorders, including granulomatosis with angiitis (5), lymphomatoid granulomatosis (6), sarcoidosis, zygomycosis, histoplasmosis, aspergillus, Pneumocystis jiroveci pneumonia, nonspecific interstitial pneumonia, pulmonary paracoccidioidomyocosis, and radiofrequency ablation. In addition to this being the first report of the atoll sign in a patient with eosinophilic pneumonia with vasculitis, the CT pattern in our patient is unique in that it seems to mock our early reliance on the atoll sign as a specific diagnostic biomarker for cryptogenic organizing pneumonia.