The radiologic findings were reviewed in nine patients with biopsy- or autopsy-proved acute interstitial pneumonia (AIP). All patients had bilateral air-space opacification on radiographs and bilateral, symmetric areas of ground-glass attenuation on computed tomographic (CT) scans. The areas of ground-glass attenuation had a patchy distribution in six patients (67%) and were diffuse in three patients. Air-space consolidation was seen at CT in six patients (67%) and involved mainly the lower lung zones in three patients and upper lung zones in one patient and was diffuse in two patients. A predominantly subpleural distribution of the consolidation was present in two patients. Eight of the nine patients died within 3 months of presentation. The authors conclude that the radiographic and CT features of AIP are similar to those of adult respiratory distress syndrome and represent acute alveolar damage. AIP differs from the more chronic forms of interstitial pneumonia in clinical presentation and in pathologic and radiologic findings.