Hypersensitivity pneumonitis (HP) is a pulmonary disease with symptoms of dyspnea and cough resulting from the inhalation of an antigen to which the patient has been previously sensitized. HP is an orphan disease, and current concepts on its diagnosis and management are often outdated. The objectives of this review are to summarize the modern evidence regarding the diagnostic criteria of HP, its pathophysiology, the procedures involved in the management of the disease, and its treatment strategies. Several areas for further research are identified, with priority given to (1) the establishment of a multicenter collaborative network to enhance the recognition, diagnosis, and management of the disease; (2) the development and support of population-based studies to provide additional insights into environmental and clinical characterization of HP; and (3) the exploration of the use and validity of biomarkers of both exposure and disease.