In response to the first cloning of a mammal from an adult cell, President Clinton asked the National Bioethics Advisory Committee (NBAC) to report to him on the legal and ethical issues that cloning raises in regard to its potential use in human beings. In its June 1997 report, NBAC agreed that creation of a human child by somatic cell nuclear transfer is scientifically and ethically objectionable at this time. This document provides an update of developments since that time. There have been a number of scientific advances in the field, many of which hold the promise of improved treatments for diseases for which there are currently no good alternatives. However, mammalian cloning has significant risks: high rates of spontaneous late-term abortions and death soon after birth, and a possible link to developmental defects in the immune system and to premature aging. Ethical concerns have caused five states and several other nations and international organizations to prohibit the cloning of human beings. Responsible public policy will need to be crafted in such a way as to prevent the use of cloning technology for unacceptable purposes, while allowing for beneficial uses that hold so much promise for curing human diseases.