In this issue we take the unusual step of publishing an “expression of concern” (p 266)1 about a paper the BMJ published in 1992,2 together with an account of our attempts to resolve the suspicions about this and other papers written by the author, Dr Ram B Singh of Moradabad, India (p 281).3 The BMJ's expression of concern coincides with a similar expression about another of Singh's papers in this week's Lancet.

As White describes in her article,3 doubts about the validity of the data in Singh's 1992 paper arose soon after we had published it—when Singh sent us a succession of other studies. The reviewers of the subsequent papers alerted us to discrepancies in the data, and to doubts about Singh's work that were already well known among researchers into diet and coronary heart disease.

What should journal editors do when confronted with such doubts? In the past, we would simply have rejected the paper. But in the wake of prominent cases of scientific misconduct in the United States in the 1970s and 1980s,4 journal editors began to recognise that they had an obligation not to ignore such doubts, an obligation now set down in the Committee of Publication Ethics code of conduct for editors.5 In practice there's a limit to what journals …