Maspin is a unique serine proteinase inhibitor that has tumor suppressor activity. It has been reported that maspin is expressed in normal human mammary epithelial cells and it is down-regulated during the progression of cancer. However, to date, there is very limited data on the clinical significance of maspin expression in human breast cancer. In this study, maspin expression was assessed immunohistochemically from 80 invasive ductal carcinoma (IDC) specimens of the breast. Also, maspin expression was compared with the clinicopathological factors (age, grade, tumor size and lymph node status), the expression of estrogen receptor (ER), progesterone receptor (PR) and p53, DNA ploidy and the overall survival in an attempt to assess its prognostic value. The maspin expression was positive in 25 IDC cases (31.3%). The maspin expression in IDC was significantly correlated with a higher histologic grade, a larger tumor size, a positive p53 status and shorter survival. There was an inverse association with maspin expression and the PR status. These findings suggest that maspin expression is not down-regulated with the progression of cancer and maspin expression may be associated with a poor prognosis. The immunohistochemical detection of maspin in breast cancers may be helpful for predicting an aggressive phenotype.