Objective To investigate the effect of mRNA expression of gelatinase A on the invasion and metastasis of human gastric carcinoma (HGC). MethodsThirtysix cases of HGC were examined by in situ hybridization technique. ResultsPositive expression rates of gelatinase A in the normal gastric tissue, peritumor tissue and HGC were 8.3%,35.7% and 83.3% respectively （P＜0.01）. The positive rates of gelatinase A in the group with serosal invasion and lymph node metastasis were 93.1% and 90.6%, much higher than those in the group with negative ones (42.9% and 25.0%).By in situ hybridization, gelatinase A mRNA was showed to be expressed in the extracellular matrix of tumor tissues,which surrounded the invasive margin of cancer tissues. The positive cells at these sites were mainly tumorinfiltrating macrophages. Conclusion There is good correlation between gelatinase A mRNA expression and the invasion, metastasis of HGC. So it can be used as a useful marker for invasion and metastasis of HGC.