The unraveling of the scientific reputation of South Korean stem cell researcher Woo Suk Hwang has taken place at startling speed. A mere few months ago, Hwang's work was the bedrock on which cloned human embryonic stem (ES) cells were advancing toward the clinic. Today, with those foundations crumbling, ES cell researchers must regroup and ponder the extent of the flaws in the South Korean work.

Hwang's exalted reputation arose from a 2004 Science paper (303, 1669–1674, 2004), considered the first convincing report of the derivation of human ES cells by somatic cell nuclear transfer. A second blockbuster paper followed in May last year (Science 308, 1777–1783, 2005), describing a remarkable improvement in the efficiency of the derivation protocol and the generation of 11 patient-specific cloned ES cell lines. Even more stunning than the first paper, the follow-up paper seemed to suggest that an exceedingly intractable technology had suddenly entered the realm of the practical.

The first signs of trouble surfaced in May 2004, when a Nature news article revealed ethical lapses in the procurement of oocytes used in the 2004 paper. Although oocyte donation by junior members of the Hwang laboratory and payment for oocytes were not expressly forbidden in South Korea at the time, Hwang's initial lack of candor and belated admission of wrongdoing ultimately forced him to resign in disgrace from his scientific leadership positions in November 2005.

Since then, attention has shifted to concerns about the scientific validity of Hwang's papers. On December 1, a report by South Korea's Munhwa Broadcasting Corporation claimed that independent tests of five of the patient-specific cell lines had uncovered potentially serious irregularities. Questions proliferated as Korean scientists pored over Hwang's data and posted their findings on a Korean-language website. Gerald Schatten, a corresponding author of the 2005 paper, after breaking publicly with Hwang in November over issues surrounding oocyte donation, announced on December 13 that he had “substantial doubts about the paper's accuracy.” Around the same time, another coauthor of the 2005 paper, Sung Il Roh, accused Hwang of multiple instances of scientific misconduct and deception. By December 16, amid a flurry of allegations and rumors, Hwang and Schatten had asked Science to retract the paper. A cloud of suspicion spread quickly to the 2004 paper and to the entirety of Hwang's scientific output.

As Nature Biotechnology went to press, it was difficult to make sense of this rapidly evolving story. Although both the 2004 and 2005 papers appear to contain misrepresentations, it is as yet unclear whether these were the result of willful fraud or simply of gross negligence in data presentation. Meanwhile, scientists and the public have been left wondering whether any cloned ES cell lines were ever produced.

We concur with the opinion of Wilmut et al. in their recent letter to Science (published online December 13, 2005) that these matters should be sorted out by scientists and not by trial in the media. At least two investigations are already underway, one by Hwang's institution, Seoul National University, and a second by the University of Pittsburgh, Schatten's employer. Whether these investigations will provide a complete accounting remains to be seen. According to one prominent stem cell researcher, skepticism that any cloned ES cells were generated is the order of the day—at least until a delegation of a half-dozen of the world's top cloning and stem cell experts has camped out in Hwang's laboratory for months and scrutinized every step of the derivation procedure. To his credit, Hwang has welcomed foreign experts into his laboratory in the past. Further international collaborative investigations could go a long way towards clearing his name.

What does the Hwang affair portend for the future of ES cell science? Rather predictably, the media have amplified the negative fallout. Equally predictably, the more measured views of scientists and their supporters have attracted less attention, leading to a misperception that stem cell scientists are, on the whole, unconcerned or aloof.

In fact, the stem cell community is keen to investigate the Hwang debacle and to assure that their field is placed on a firm ethical footing. The absence of federal leadership in the United States is due in large measure to the obstructionist policy of the present administration. Seeking to fill the void, the US National Academies has worked to formulate appropriate guidelines for the conduct of research on human ES cells (Nat. Biotechnol. 23, 793–794, 2005). One of the Academies' key recommendations is that institutions provide a new layer of review through Embryonic Stem Cell Research Oversight (ESCRO) committees. Since the release of the Academies' report in March 2005, ESCRO committees have been set up in several major US research institutions and are actively vetting research protocols. More recently, the International Society for Stem Cell Research has responded to the Hwang news by forming a task force to define internationally acceptable guidelines for ES cell research.

Although the Hwang affair is clearly a setback for the field, it is at the same time a powerful argument for the need to aggressively develop ES cell technology in countries where such research is subject to much more stringent ethical and scientific oversight. Indeed, these unfortunate events expose the dangers and the foolishness of entrusting a technology of immense promise to a single laboratory in a single country. What happened in South Korea has little bearing on the therapeutic potential of ES cells or on the value of research being done elsewhere. The failings of one group should not be used to sully the efforts of other groups. Whereas it remains possible that more judicious peer review by the Science referees could have caught some of the deficiencies of Hwang's papers before publication, the true test of a scientific advance has been, and always will be, replication by multiple investigators. It's time to get on with it.