Therapeutic intervention against exaggerated cytokine activity has been proved to be clinically successful in several serious, inflammatory disorders [reviewed in 1, 2] in the last decade. Half a million patients with chronic arthritis have shown tremendous improvement with tumour necrosis factor (TNF)- or interleukin (IL)-1-blocking treatment. Similarly anti-TNF therapy is beneficial for chronic inflammatory bowel disorders such as Crohn's disease. The success of this novel strategy has generated a search for additional endogenous mediators suitable for therapeutic targeting. The high mobility group box protein 1 (HMGB1) is a lately discovered candidate molecule identified as an important extracellular mediator in local and systemic inflammation in both human and experimental diseases such as, e.g., arthritis and sepsis [3]. Therapeutic neutralization of HMGB1 has shown encouraging results in experimental disease models, but has not yet reached clinical trials. This volume of the Journal of Internal Medicine contains a collection of four reviews addressing novel aspects of HMGB1 biology of potentially clinical interest. The manuscripts are the product of a recent meeting entitled the 'First HMGB1 Cytokine World Congress' sponsored by the Journal of Internal Medicine.