The recent introduction of new US Food and Drug Administration-approved medications for the treatment of idiopathic pulmonary fibrosis/usual interstitial pneumonia raises important concerns about the accuracy of diagnosis. The term honeycomb lung, used widely by radiologists and pathologists in the diagnosis of usual interstitial pneumonia, represents a late stage of the disease and conveys no biological information. A new conception of end-stage lung disease in usual interstitial pneumonia, based on the dying back of the pulmonary acinus, is proposed, which may improve the sensitivity and specificity of the diagnosis and provide an understanding of its pathogenesis.