Purpose : To describe HRCT findings in five patients with pathologically proved acute interstitial pneumoniaMaterials and Methods : This study included 5 patients with pathological and clinical diagnosis of acuteinterstitial pneumonia. Mean age of the patients was 40(range, 31-53 years). CT scans were reviewed by two chestradiologists retrospectively. CT scans were assessed for the presence and distribution of ground-glassattenuation, air-space consolidation, interlobular septal thickening, honeycombing, and pleural effusion. Results: The area of ground-glass attenuation and air-space consolidation were seen at HRCT in all 5 patients. Theselesions were distributed diffusely in both lungs, but involved predominantly subpleural lungs in 2 patients andposterior lungs in 3 patients. Three patients had mild interlobular septal thickening. None of them showedhoneycombing. Three of the 5 patients died within 52 days of initial manifestation. Conclusion : Acuteinterstitial pneumonia differs from the more chronic form of idiopathic interstitial pneumonia in their HRCTfindings.