The online version of this editorial by Myra McClure and Simon Wessely contains an error (BMJ 2010;340:c1099, doi:10.1136/bmj.c1099). We misinterpreted an author’s proof comment relating to the eighth paragraph, which should read: “Meanwhile, a different strategy is also being considered to reconcile these different findings: that new blood samples should be taken from patients with diagnosed chronic fatigue syndrome and sent to laboratories capable of carrying out the analysis. This is likely to happen [not “This is unlikely to be soon”].