Intravenous fentanyl citrate has stood the test of time as a valuable formulation for pain management. The desirable physicochemical properties of fentanyl have allowed the development of several alternative formulations for delivery using less invasive routes, for example, transmucosal (intranasal, oral buccal and oral sublingual) and transdermal. These new formulations have been applied to clinical settings in which rapid onset of analgesia is desired, using convenient but noninvasive methods. Recent commercialization of various formulations has been driven largely by the needs of cancer patients, for whom severe but self-limiting "breakthrough" pain is less suitably treated by parenteral or oral routes of opioid administration. However, these formulations are also used for acute analgesia in prehospital and in-hospital emergency department care, and for pediatric acute pain management. Finally, they are increasingly used by patients with chronic pain of nonmalignant origin, although there is considerable debate about their merit in this group. We searched the databases MEDLINE, PubMed, EMBASE, CINAHL and Cochrane up to October 2011, using search terms "fentanyl AND nasal; intranasal; transmucosal; buccal; sublingual; oral; inhaled; inhalation; transdermal" The characteristics of several formulations of fentanyl are reviewed, detailing their pharmacokinetics, pharmacodynamics and clinical experience with their use for acute pain management.