High Mobility Group Box 1 (HMGB1), a highly conserved protein, plays key roles in acute sepsis and in chronic inflammatory diseases including cancer, diabetes and Alzheimer’s disease. Intracellularly, HMGB1 binds DNA, modifies its structure  and assists with the regulation of transcription. Extracellularly, HMGB1 is released either actively or passively from damaged necrotic cells. It thereby promotes inflammatory responses by numerous mechanisms, including by binding to key pattern recognition receptors such as the Receptor of Advanced Glycation End-products (RAGE). Thus, control of the HMGB1-receptor interactions represents a promising therapeutic approach for the treatment of a number of inflammatory based diseases. In this study, using a Surface Plasmon Resonance (SPR) approach, we have discovered that HMGB1 self-associates to form dimers and tetramers with high affinity in a highly-specific manner. The self-association is markedly influenced by ionic strength, the level of oxidative stress and the presence of zinc ions. We have developed a novel molecular model which explains how zinc coordinates two HMGB1 molecules as a dimer. The role of the self association of HMGB1 in binding DNA or RAGE is now under investigation.