目的 :检测基质金属蛋白酶（ matrix metalloproteinase 9,MMP－ 9）在各类人胃粘膜中的表达频率，并观察其分布特点及其与胃癌发生和发展的关系。材料和方法：采用免疫组织化学染色，组织选择性蛋白提取法 /Western印迹杂交和酶谱分析等方法，检测 27例非癌胃粘膜， 52例各类癌前病变和 65例胃癌标本以及 2株胃癌细胞系中 MMP 9的表达情况。 结果： MMP 9的检出率在非癌粘膜为 3.7％ (1/27)，萎缩性胃炎 69.2％ (9/13） ,肠上皮化生 70.0％ (7/10),Ⅱ型和Ⅲ型非典型增生分别是 86.7％ (13/15)和 78.6％ (11/14)；它在高、中、低和未分化胃癌中的表达率分别达 64.2％ (9/14）、 78.6％ (11/14)、 83.3％ (20/24)和 76.9％ (10/13)。 MMP 9在两株细胞系以及肿瘤间质纤维细胞亦呈阳性。结论 :MMP 9表达出现在胃癌发病的早期阶段；其表达率与胃癌进展正相关（ P<0.01) Objective : To detect the expression frequency of matrix metalloproteinase 9 (MMP-9) in various types of human gastric mucosa, and observe its distribution characteristics and its relationship with the occurrence and development of gastric cancer. Materials and methods: Immunohistochemical staining, tissue-selective protein extraction/Western blot and zymography were used to detect 27 cases of non-cancerous gastric mucosa, 52 cases of precancerous lesions and 65 cases of gastric cancer specimens and 2 specimens. The expression of MMP 9 in gastric cancer cell lines. Results: The detection rate of MMP 9 was 3.7% (1/27) in non-cancerous mucosa, 69.2% (9/13) in atrophic gastritis, 70.0% (7/10) in intestinal metaplasia, and type II and type III SARS. Types of hyperplasia were 86.7% (13/15) and 78.6% (11/14) respectively; its expression rates in high, middle, low and undifferentiated gastric cancer were 64.2% (9/14) and 78.6% (11/ 14), 83.3% (20/24) and 76.9% (10/13). MMP 9 was also positive in both cell lines and tumor interstitial fibroblasts. Conclusion: The expression of MMP 9 was found in the early stage of gastric cancer; its expression rate was positively correlated with the progression of gastric cancer (P<0.01).