目的　研究SARS肺部病变形态特征和探讨胶原纤维在SARS肺部病变中的变化规律。方法　 4例SARS肺标本组织 ,经HE、苦味酸天狼猩红和免疫组化染色、光镜或偏振光观察胶原纤维的分布及表达。结果　SARS肺部病变发展过程分 3期 :急性渗出期、纤维增殖期、胶原化期。急性渗出期 :胶原纤维较正常稍增多 ,可见Ⅰ、Ⅲ、Ⅳ型 ,Ⅰ型较多 ;纤维增殖期 :Ⅰ、Ⅲ、Ⅳ型胶原纤维增多 ;胶原化期 :基膜及肺间质Ⅳ型胶原显著增多 ,而Ⅰ型胶原明显减少。结论　胶原纤维过度增生及代谢异常是导致肺纤维化重要因素之一 ,苦味酸天狼猩红和免疫组化联合应用对认识胶原纤维的变化规律起到互补作用 Objective To study the morphological characteristics of lung lesions in SARS and to explore the changes of collagen fibers in lung lesions of SARS. Methods The distribution and expression of collagen fibers in 4 SARS lung specimens were observed by HE, picric Sirius red and immunohistochemistry, light microscope or polarized light. Results The development of SARS pulmonary lesions in three phases: acute exudative period, fiber proliferation period, collagenization period. Acute exudative period: collagen fibers increased slightly than normal, showing Ⅰ, Ⅲ, Ⅳ type, type Ⅰ more; fiber proliferative phase: Ⅰ, Ⅲ, Ⅳ collagen fibers increased; collagenation period: basement membrane and interstitial lung Ⅳ Type collagen increased significantly, while type Ⅰ collagen decreased significantly. Conclusion Collagen hyperplasia and metabolic abnormalities are one of the important factors leading to pulmonary fibrosis. The combined application of picric sirius red and immunohistochemistry plays a complementary role in understanding the variation of collagen fibers