The absence of superimposition of parenchymal structures on HRCT permits better assessment of the pattern and distribution of disease than is possible on the radiograph. Several studies have shown that HRCT is superior to the chest radiograph in the diagnosis and management of patients with chronic interstitial lung disease. High-resolution studies may demonstrate extensive parenchymal disease when the radiograph is normal and allow for a confident diagnosis when the radiographic findings are nonspecific. It is superior to the chest radiograph in determining whether transbronchial or open lung biopsy is indicated, and it is essential in selecting the optimal biopsy site. Although further studies are required to determine the precise role of HRCT in interstitial lung disease, current indications for HRCT include: (1) assessment of patients with symptoms suggestive of infiltrative lung disease but normal or nonspecific findings on the radiograph; (2) further evaluation of the lung parenchyma in patients in whom the radiographic findings are not in keeping with the clinical history or symptomatology; (3) as a guide to the optimal biopsy site in all patients undergoing open or transbronchial biopsy; and (4) assessment of suspected complications (e.g., infection) in patients with diffuse lung disease.