Diagnosing the range of pulmonary disorders caused by Aspergillus spp can be challenging. In instances of hypersensitivity responses to Aspergillus spp (ie, allergic bronchopulmonary aspergillosis, bronchocentric granulomatosis, and hypersensitivity pneumonitis), the surgical pathologist must be cognizant of their relationship to infection, as fungal organisms may be rare or absent from the biopsy specimens. Within the spectrum of opportunistic infection, it is critical to distinguish Aspergillus spp from other fungal mimics, as well as to discern whether infection is limited, progressive, or immanently life threatening. However, the surgical pathologist who establishes expertise in this area will be rewarded by the satisfaction of having contributed primarily to an important area of patient care. This article reviews the spectrum of pulmonary disorders due to infection by Aspergillus spp, with emphasis on the clinical implications of diagnosis.