Purpose To investigate the pathologic characteristics of severe acute respiratory syndrome(SARS). Methods Three lung tissues from SARS patients were stained by HE and immunohistochemical S P method for the expression of CK, CD34, type Ⅳ collagen, CD68, and Mac387. Results Alveolar epithelia were destroyed extensively, while type Ⅱ alveolar epithelia showed hyperplasia. There were swelling of the capillary vessel endothelia of alveolar wall and hyaline membrane formation in most of the pulmonary alveolar...