The epithelial glycoprotein Ep-CAM is overexpressed in colon cancer and breast cancer. We assessed the frequency and prognostic significance of Ep-CAM in tissue specimens from 205 patients with invasive breast cancer, by immunohistochemical staining with a monoclonal antibody specific for the Ep-CAM antigen. Ep-CAM overexpression was found in 35.6% of samples and was associated with poor disease-free and overall survival.