Opioid agonists-antagonists are defined as opioids with mixed actions. These drugs include agents with agonist-antagonist properties (substances such as nalorphine or pentazocine that appear to be agonists at some receptors and antagonists or very weak agonists at others) and the partial agonists (such as buprenorphine). This article is a current review of recent studies investigating agonist-antagonists for use in clinical medicine.