Aim: to assess the expression ofcathepsin B(ctsB; an important protease) in human breast cancer and correlate that with the tumor grade. Materials and Methods:Serial sections were obtained from 23 formalin-fixed paraffin embedded breast cancer tissue specimens which were collected from Alasad University Hospital and a pathological laboratory in Lattakia - Syria. Tissues were stained for cathepsin B using immunohistochemistry. Tonsil tissues were also included as a positive control. Results:Positive cytoplasmic staining of CtsB was observed in both follicular macrophages and endothelial cells in tonsil sections. In breast cancer tissues, tumor cells, endothelial cells and stroma stained positive for CtsB. The presence of CtsB in blood endothelium significantly correlated with the tumor grade (p=0.049). Conclusion: These results supported the important role of cathepsin B in tumor progression, particularly in angiogenesis. Future studies should investigate the regulating mechanisms of cathepsin activities within the tumor environment, and that can be considered as new tagets for cancer treatment.