Introduction: Certain blood group is an important risk factor for some malignancies like pancreatic, kidney, urinary bladder, cervix and stomach. Carcinoma of breast is the most common malignancy among urban Indian females and second commonest in rural India and the incidence is continuously increasing.

Aim: to study prevalence of ABO blood group in patients of carcinoma of breast.

Method and Material: This is a cross sectional, hospital based study, conducted in Gujarat Cancer Research Institute, Ahmedabad, Gujarat. 303 women who were diagnosed as carcinoma of breast included in this study from the GCRI hospital, Ahmedabad. Reports of Biopsy and blood group investigation were collected.

Result:  Out of 303 women of carcinoma breast, patients having blood group A was 125, B was 110, AB was 16 and O was 52.therefore Breast malignancy in patients having blood group A (41.25%) is higher as compared to B (36.30 %), AB (5.28%) and O (17.16%).Thus the risk of developing breast malignancy in the blood group A is more than blood group B, O and AB.

Conclusion: The most vulnerable blood group regarding breast malignancy is found to be blood group A as compared to B, AB and O.