Abstract: Objective 　To explore the correlation between expression of plexin-B1 and metastasis of human breast cancer. Methods 　Expression levels of plexin-B1 were examined in 15 normal breast specimens and 85 surgically resected breast cancer specimens by supervision immunohistochemistry. Results 　The expression of plexin-B1 in 15 normal breast specimens was completely negative. In breast cancer specimens the expression rates of plexin-B1 were 76. 5 %(65/ 85) in the carcinoma nests cells and 70. 6 %(60/ 85) in lymphatic endothelial cells respectively. The percentage of plexin-B1 positive cells was significantly higher in carcinoma nest s of tumors with metastasis (87. 0 %, 47/ 54) than those without (58. 1 %, 18/ 31), as well as in lymphatic endothelial cells with (85. 2 %, 46/ 54) than those without metastasis (45. 2 %, 14/ 31) . The expression of plexin-B1 is st rongly correlated with the ER status. Significant positive correlation ( r = 0. 666, P < 0. 01) of the plexin-B1 expression was found between carcinoma cells and lymphatic endothelial cells. No significant correlation was found between plexin-B1 expression level and tumor size or positive lymph nodes or tumor stage. Conclusion 　The high expression of plexin-B1 may be strongly correlated with the process of breast cancer progression and metastasis.