Prognostic factors, e.g. metastatic disease, lymph node status, tumour size, histologic grade, estrogen and progesterone receptors, and markers of proliferation are used to predict the clinical course of breast cancer at the time of primary treatment. Patients with a poor prognosis are offered adjuvant therapy. For the choice of adjuvant therapy (endocrine or cytotoxic) treatment predictive factors, e.g. estrogen and progesterone receptor; are useful. Putative new prognostic factors (e.g. oncogenes, tumour suppressor genes, and invasive factors) should be evaluated together with the clinical established factors in multivariate analyses.