Recent scientific achievements in cell and developmental biology have provided unprecedented opportunities for advances in biomedical research. The demonstration that fully differentiated cells can reverse their gene expression profile to that of pluripotent cells, and the successful derivation and culture of human embryonic stem cells (ESCs) have fuelled hopes for applications in regenerative medicine. Ethical issues concerning the use of cloned human embryos for the derivation of stem cells have stimulated the search for alternative methods for reversing differentiated cells into pluripotent cells. The present state of these reprogramming technologies will be reviewed and their relative success will be discussed.