Abstract: Objective: To detect the expression of the cellular adhesion molecule CD138 and anti-apoptotic gene bag-1 in breast cancer and to investigate its clinical significance. Methods: A total of 100 paraffin-embedded breast cancer specimens were screened for expression of CD138 and bag-1 with immunohistochemistry. The related clinicopathological data were collected. The relationship of the expression of CD138 and bag-1 with the clinicopathological features was analyzed. Results: 1) The rate of expression of CD138 was lower in cancer tissues (46.0%) than in normal breast tissues (100%)(P<0.01). The rate of expression of bag-1 was higher in cancer tissues (76.0%) than in the normal breast tissues (15.0%)(P<0.01). 2) The expression of CD138 and bag-1 was correlated with lymph node metastasis but was not correlated with pathological type, clinical staging, or expression of estrogen receptor. 3) The expression of bag-1 was significantly negatively correlated with that of CD138 (P<0.01). Conclusion: Breast cancer tissues present with decreased expression of CD138 and increased expression of bag-1. CD138 and bag-1 may play important roles in the development of breast cancer and can be used as biological markers for breast cancer diagnosis and prognosis.