The Journal of Physiology has been informed by Bente Klarlund Pedersen, MD, DMSc, Professor of Integrative Medicine, Director of the Centre of Inflammation and Metabolism, Department of Infectious Diseases and CMRC Rigshospitalet at the University of Copenhagen Faculty of Health Sciences, Copenhagen, Denmark, of concerns about the validity of some of the data contained in an article published in the journal (Akerstrom T, Steensberg A, Keller P, Keller C, Penkowa M, and Pedersen BK. Exercise induces interleukin-8 expression in human skeletal muscle. J Physiol March 1, 2005; 563(Pt 2), 507–516; published ahead of print December 23, 2004, doi:10.1113/jphysiol.2004.077610) and informed us that this matter is being investigated as part of a larger investigation into a more extensive body of published work. While awaiting the outcome of our investigations and further correspondence with the authors, The Editor-in-Chief, David J Paterson, wishes to notify readers of our concerns regarding this article.