A major focus within the modern bioethics debate has been on reshaping power relationships within the doctor-patient relationship. Empowerment of the vulnerable has been achieved through an emphasis on human rights and respect for individual dignity. However, power imbalances remain pervasive within healthcare. To a considerable extent this relates to insufficient attention to social injustice. Such power imbalances together with the development of new forms of power, for example through new genetic biotechnology, raise the spectre of increasing social injustice. Attention will be drawn to the need to extend the bioethics debate to include ethical considerations regarding public health. Changes in political philosophy will also be required to reshape international power relations and improve population health.