Having established prolactin to be an indicator of disease progression and hyperprolactinemia as an independent predictor of short term prognostication, we have in this report compared plasma prolactin with the expression of c erb B-2 oncoprotein, ER and PR. c erb B-2 oncoprotein, ER and PR are determinants of breast cancer biology. This is a retrospective study of 47 breast cancer patients. When patients were grouped according to the stage of the disease, plasma prolactin was higher in patients with advanced disease than those with stage II disease. The patients were sub-grouped according to prolactin < 20.0 ng/ml and > 20.0 ng/ml. The expression of c erb B-2, ER and PR did not differ in these two sub-groups. The overall survival differed significantly between the two sub-groups of prolactin. The patients were sub-grouped according to c erb B-2 positivity or negativity, there was no significant difference in survival. c erb B-2 expression did not differ between the three grades of the tumor, nodal and receptor positivity or negativity. Hence, the present study reinforces the positive association between hyperprolactinemia and unfavourable prognosis and finds c erb B-2 expression as a weak prognosticator in advanced breast cancer patients.