Buprenorphine, a mixed agonist-antagonist opioid (or partial agonist), is a safe and effective treatment for opioid dependence. However, there is concern that buprenorphine may be abused due to its high abuse potential. A sublingual buprenorphine/naloxone combination tablet may reduce the risk of abuse associated with buprenorphine alone. The purpose of this study is to determine the abuse potential of acute doses of buprenorphine/naloxone in individuals who are maintained on different daily doses of sublingual buprenorphine/naloxone.