Ethical debate surrounding human enhancement, especially by biotechnological means, has burgeoned since the turn of the century. Issues discussed include whether specific types of enhancement are permissible or even obligatory, whether they are likely to produce a net good for individuals and for society, and whether there is something intrinsically wrong in playing God with human nature. We characterize the main camps on the issue, identifying three main positions: permissive, restrictive and conservative positions. We present the major sub-debates and lines of argument from each camp. The review also gives a flavor of the general approach of key writers in the literature such as Julian Savulescu, Nick Bostrom, Michael Sandel, and Leon Kass.