In vitro fertilization (IVF) stands out as one of the contemporary period's most extraordinary technologies, and its social and ethical consequences among the most far reaching. Despite its uncertain effectiveness and medical consequences, IVF has contributed significantly to the medicalization of infertility and the increasingly imperative character of reproductive technology. New developments in IVF, particularly oocyte donation, have created new definitions of treatable infertility and new social needs for IVF; when the technology does not result in pregnancy or healthy babies, these developments have created profound new disappointments. IVF and the commodification of the extracorporeal embryo have also confused the social meaning and legal definition of parenthood. Ultimately the relationship between prospective parents, infertility specialists, and the embryos that they create is a highly ambiguous one. This ambiguity is likely to be a long-term characteristic of efforts to develop, use, and assess assisted reproductive technologies.