The clinical practice guidelines for hypersensitivity pneumonitis have been independently published by the American Thoracic Society (ATS) and American College of Chest Physicians (Chest), and both address nonfibrotic and fibrotic hypersensitivity pneumonitis. Both guidelines also emphasize the distinction between fibrotic hypersensitivity pneumonitis and idiopathic interstitial pneumonias, especially idiopatic pulmonary fibrosis. The typical pathological features of fibrotic hypersensitivity pneumonitis consist of fibrosing interstitial pneumonia, airway-centered fibrosis, and poorly formed granulomas. These guidelines emphasize the importance of multidisciplinary discussions among clinicians, radiologists, and pathologists in order to achieve adequate treatment, based on the history of antigen exposure, the high-resolution computed tomography (HRCT) findings, bronchoalveolar lavage lymphocytosis, and the histopathological findings.