If human cloning is to become a reality, the preimplantation geneticist must be responsible for determining the indications for undertaking cloning and for establishing the risks and benefits of human cloning. The unresolved issue is whether a compelling argument can be made for cloning a human for therapeutic reasons while outweighing legal, moral and ethical objections. At present, 'whole person' cloning does not seem justified under any circumstance, whereas cloning for the replacement of diseased cells, tissues or organ systems, i.e. 'spare parts', seems to be a likely, acceptable application of cloning strategies for humans.