Abstract: Objective :To probe the MDR-1 mRNA expression of primary tumor and metastatic lymph node of patients with breast cancer,and the relations between gene expression and clinical pathological features. Methods :The reverse Transcription-PCR technique was used to detect the MDR-1 mRNA expression of primary tumor and metastatic lymph nodes of 30 cases of patients with breast cancer,and the relations between gene expression and clinical pathological features were investigated. Results :The expression level of MDR -1 mRNA of primary tumor was significantly higher than that of metastatic lymph nodes. Conclusion :It was suggested that the positive rate of MDR-1 mRNA expression is higher in primary tumor than that of metastatic lymph node. MDR-1 mRNA expression in primary tumor is correlated with age and TNM staging, and it is not related to the size of tumor and extent of lymph node metastasis.