The wide spectrum of disease states caused by fungi of the genus Aspergillus is dependent in large measure on environmental conditions leading to exposure, and to local and systemic host defenses. Allergic aspergillosis occurs in individuals hypersensitive to the fungus and is treated by immunosuppression, whereas invasive aspergillosis predominates in the severely immunocompromised and is treated with antifungal therapy. Aspergillomas generally arise from saprophytic colonization of a pre-existing pulmonary cavity with Aspergillus, and may be complicated by life-threatening hemoptosis.