One hundred breast cancer patients, 35 adjuvant and 65 advanced, were interviewed 0-24 months after the start of chemotherapy to assess their knowledge and perceptions of the purposes, risks and benefits of treatment. Prior to therapy, all had been given verbal explanations and had signed informed consent forms explicitly detailing drugs, objectives and possible adverse effects of therapy. Seventeen percent of adjuvant and 29% of advanced patients were unable to name any of their drugs. While most patients recognized distressing side effects such as nausea and hair loss, less than 50% were aware of the potentially lethal complications of infection and bleeding. While the purpose of adjuvant therapy was cure, only 29% of the adjuvant patients were aware of this. In contrast, 35% of the advanced patients incorrectly stated that they were told their therapy was potentially curative. Explanations given by a nurse in addition to a physician were better understood than those given by a physician alone. We conclude that, in spite of intensive efforts at improving informed consent procedures, current results are unsatisfactory.