Stem cell research that requires the destruction of human embryos is incompatible with Catholic moral principles, and with any ethic that gives serious weight to the moral status of the human embryo. Moreover, because there are promising and morally acceptable alternative approaches to the repair and regeneration of human tissues, and because treatments that rely on destruction of human embryos would be morally offensive to many patients, embryonic stem cell research may play a far less significant role in medical progress than proponents believe.