The cloning of Dolly the sheep gave rise to a widespread call for limits on interference with life. Until recently, the main limits were technical: what it is possible to do. Now scientists are faced with ethical limits as well: what it is acceptable to do. In this context, we take ethics to involve systematic and rational reflection on moral issues raised in the public sphere. The concerns of the general public are not necessarily valid, but they are the best point of departure if the discussion is to lead to a socially robust framework for setting limits to the use of animal biotechnology. To assess public understanding, we examine two sources of data: Eurobarometer surveys from 1991 to 2002 and a qualitative interview study carried out in Denmark in 2000. Based on these sources, we formulate, and then discuss closely, the following concerns: dangers to human health and the environment, animal welfare, animal integrity, and usefulness. In the final part of the article, it is proposed that a principle of proportionality should be the foundation for socially robust applications of animal biotechnology. Only in cases where the usefulness of the technology can be said to outweigh countervailing moral concerns, as in biomedical research, will applications of animal biotechnology stand up to scrutiny in the public sphere.