High-resolution computed tomography (HRCT) was performed on 15 patients who had diffuse peripheral lung disease, and the findings were compared with those of conventional chest radiography and histologic examination. Bullae, interstitial fibrosis with honeycombing, and small granulomas were more clearly and specifically demonstrated on HRCT scans than on conventional chest radiographs in all patients. Histologically proved mild alveolar wall thickening due to alveolitis in cases of sarcoidosis and systemic lupus erythematosus was not detected. HRCT is useful for performing detailed morphological analyses of abnormalities of the peripheral portions of the lung.