THE EDITOR RESPONDS: Thank you for your letter, Paul. We did not mean to imply that research using embryonic stem cells has no ethical dimension, or to take a particular ethical position. In fact, most of the article was devoted to the progress made using non-embryonic stem cells. However, given the limits of space in the magazine and the complexity of the ethical debate around stem cells, we chose to report only on the research itself. We would urge readers to investigate the matter for themselves, from a variety of perspectives.