Pluripotent stem cells hold promise for transplantation therapy to treat degenerative diseases, but isolating a patient's stem cells may pose a technical limitation. In the April 27 Science, Wakayama et al. describe the application of cloning to generate embryonic stem (ES) cells (Science 2001, 292:740-743). The authors used nuclei from adult-derived somatic donor cells of five different strains of mice to produce cloned blastocysts. These were then used to derive 35 different nuclear transfer ES (ntES) cell lines. The pluripotency of the ntES cells was assessed by in vitro differentiation. The ntES lines could be differentiated into dopaminergic and serotonergic neurons. Blastocyst injection of ntES demonstrated that the ntES cells contribute extensively to many tissues in vivo, including male and female germ cells. The efficient pluripotency of such cloned ntES cells offers promise for future therapeutic cloning applications.