Objective： To investigate the mRNA expression of ADAM8 in Breast cancer and the roles of ADAM8 in tumorigenesis and progression of Beast cancer．Methods：The ADAM8 mRNA expression in 39 breast cancer and 19 normal breast tissues was detected by flurence-quantitative RT-PCR, and the expression levels of ADAM8 were correlated with patients’clinical and pathological parameters. Results：Repressed ADAM8 mRNA expression was found in the 39 breast cancer tissues compared with that in 19 normal breast tissues（P=0．015)．Furthermore, lower level of ADAM8 mRNA expression was found in stageⅡb、Ⅲ than in stage Ⅰ、Ⅱa，and the breast cancer tissues with positive lymph node metastasis exhibited less ADAM8 mRNA expression than those without lymph node metastasis, although this difference did not reach significant level (P>0．05). Conclusions：ADAM8 mRNA was lower expressed in breast cancer. Reduced or losed expression of ADAM8 gene may be involved in the pathogenesis and progress of this disease.