Context .- Idiopathic bronchiolocentric interstitial pneumonia, airway-centered interstitial fibrosis, centrilobular fibrosis, and bronchiolitis interstitial pneumonia are increasingly recognized histopathologic variants of idiopathic interstitial pneumonia that are difficult to fit within existing classification schemes. Objective .- To review and analyze the appropriate literature that describes the spectrum of histopathologic changes in these conditions, in an effort to ascertain similarities as well as their differences. In addition, we examined associations with hypersensitivity, cigarette smoking, and survival data. Data Sources .- Relevant and peer-reviewed literature indexed in PubMed (National Library of Medicine) coupled with experience gained by review of personal cases with appropriate histopathology constitute the basis of this study. Conclusions .- As anticipated, the common link among the above-cited conditions is their bronchiolocentricity, with a predominance of either fibrosis or inflammation. Clear-cut associations with hypersensitivity or cigarette smoking are not evident in this study. The airway-centered interstitial fibrosis variant of bronchiolocentric interstitial lung disease appears to have a poor outcome.