In the paper by Nikolaus et al(Gut 2002;52:1286–90, “Interferon ß-1a in ulcerative colitis: a placebo controlled, randomised, dose escalating study”) an exploratory study in 17 patients is reported. In the paper a p value for the comparison between remission in the IFN group (3/10) and the placebo group (0/7) is quoted with 0.023. This is an error and should be 0.23. The conclusions (“Patients treated with escalating doses of IFN-ß-1a tended to show higher clinical response and remission rates than those receiving placebo, although the differences between the groups did not reach statistical significance”) remain correct, as they were not based on any statistical significance.