Peritoneal metastasis of colorectal cancer is a major clinical issue and results in poor prognosis for patients after surgical resection. Here, we found that abdominal surgery trauma induced high release of high-mobility group box I (HMGB1) in the peritoneal cavity of mice. Recombinant HMGB1 injected in the peritoneal cavity recruited abundant myeloid derived suppressor cells (MDSCs) after the surgical trauma. HMGB1 Box-A and gemcitabine reduced the recruitment of MDSCs in the peritoneal cavity after the operation and ameliorated the peritoneal metastasis burden of colon cancer in mouse model. These results showed that abdominal surgery trauma leads to a large amount of HMGB1 released in the peritoneal cavity which recruits numerous MDSCs to promote peritoneal metastasis of colon cancer after curative surgery. (C) 2013 Elsevier Inc. All rights reserved.