Epigenetics is a growing field of study in which there are genetic modifications that do not involve changes to base sequences in a gene, but that result nonetheless in changes to gene expression. It has long been known that changes in gene expression play an important role in the establishment of pain states. But it is not known whether a priming injury can induce lasting epigenetic marks which would result in an increase in both postoperative acute pain and the risk for chronic pain. Only by fully understanding these epigenetic mechanisms will we be able to offer better drugs for the treatment of pain, and to identify those at high risk of postoperative pain and postsurgical chronic pain.