How might a global bioethics account for profound cultural difference in a world marked by porous borders? The authors endorse a critical, self-reflexive bioethics, suggesting that bioethics needs to change its fundamental orientation if it is going to remain relevant and intellectually vibrant throughout the twenty-first century. Bioethics must attend to issue of social justice and public health, while seriously considering the implications of social context for medical morality. Negotiating moral consensus across cultural boundaries will be difficult, but is is more likely to succeed if we critically engage with the cultural assumptions underlying bioethics itself.