The present study investigated the expression of Cathepsin-D in breast tumours regarding the histological types, grades, and pathological types. This study was carried and investigated the expression of Cathepsin-D in 80 cases of breast carcinomas and 10 control cases. Sections were stained by hematoxylin and eosin for diagnosis and typing of breast diseases and by avidine-biotin immunoperoxidase for immunostaining of Cathepsin-D. Expression of Cathepsin-D immunoreactivity was confirmed in this study. A significant correlation was detected between Cathepsin-D and both tumour size and degree of tumoral differentiation of infiltrating duct carcinoma. No significant correlation was detected between Cathepsin-D and metastatic lymph nodes, age group, different histological types andtumour associated stroma. Cathepsin-D in human breast cancer cells play an active role in the tumour progression that leads to metastasis. It also plays a role in the stimulation of growth and dessimination of cancer cells via production of growth factors.