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by Woo Suk Hwang and his colleagues on patient-specific embryonic stem cells created by somatic cell nuclear transfer (“Editorial retraction, ” D. Kennedy, 20 Jan., p. 335) in South Korea undermine the credibility of the nascent, and fragile, stem cell field. These unfortunate circumstances may embolden opponents of embryonic stem cell research who have argued against such research based on moral objections and on mistrust of scientists to monitor their own activities and ambition. Excesses in high-profile biomedical re-search are regrettably not new. The history of the gene therapy field provides one perspec-tive. Soon after cloning of mammalian genes first became possible, expectations were raised that gene therapy might be used to treat serious genetic disorders, such as hemoglobin dis-eases, cystic fibrosis, and cancer among oth-ers. After a flurry of initial clinical experi-ments in gene therapy that led to unsubstanti-ated claims or lack of objective findings, a panel was convened by the NIH Director Harold Varmus in 1995 to assess the state of the field (1). This group described a field in which research findings were oversold, expec-tations were raised beyond what was reason-able at the time, and scientific rigor was relaxed in the enthusiasm to rush ahead. If gene therapy and stem cell fields have ele-ments in common, what does recent history sug-gest for the future? Since 1995, progress in gene therapy has been episodic, yet clearly on a posi-tive trajectory. In an elegant study reported in 2000, Fischer and his colleagues provided evi