: Gene-expression profiles are a promising development in determining the prognosis of patients with primary breast cancer. They accurately assess the risk on distant recurrence of disease and show if the patient might benefit from adjuvant therapy after surgery thus minimising the risk of distant metastases. Three clinically relevant profiles on prognosis have now been published, two of which come from the Netherlands, and whose results are an improvement on those using traditional clinical parameters i.e. the St. Gallen and the National Institutes of Health criteria. These gene-expression profiles mean that 25-40% of patients need no longer undergo adjuvant systemic therapy (chemotherapy and/or endocrine therapy). Although the risk-stratifying power of these profiles has been established, their power in predicting the response of the patients to adjuvant systemic therapy still awaits scientific proo