Biotechnologies already on the horizon will enable us to be smarter, have better memories, be stronger and quicker, live longer, be more resistant to diseases, and enjoy richer emotional lives. Allen Buchanan explores urgent ethical issues raised by these developments, about what it is to be human and what sort of society we should strive to have. Whether or not the benefits are worth the risks, Buchanan's thought-provoking work deserves careful consideration.