High Mobility Group Box 1 is a non-histone chomosomal protein that functions in endotoxin lethality. It is released from activated macrophages and is present at elevated levels in the serum of sepsis patients. HMGB1 was also reported to interact with RAGE (receptor for advanced glycation end products) and to influence neuron development.A large number of sequences related to the cDNA for HMG1 protein hampered the cloning and mapping of the active HMG1 gene. Ferrari et al. (1996) showed that the HMG1 gene contains introns, whereas the HMG1-related sequences do not and most likely are retrotransposed pseudogenes. They identified 8 YACs from the ICI and CEPH libraries that contain the human HMG1 gene. The gene is similar in structure to the previously characterized mouse homolog.