Remifentanil (R) is a novel short-acting mu-receptor opioid. R is in the same structural family as fentanyl and the other phenylpiperidines, but it differs from fentanyl because of its pharmacokinetic profile and its metabolism: R undergoes extrahepatic metabolism by blood and tissue nonspecific esterases. For these reasons the time required for decreases of any percentage plasmatic concentrations of R after termination of the infusion is independent of infusion duration. The pharmacokinetic profile of R is organ-independent and the dosing regimen must be regulated in elderly patients by reducing the bolus and infusion doses, and in obese subjects by calculating the intravenous dosages as a function of age and lean body mass. The placental transfer of R doesn't affect the newborn as recently described in literature but further and wider clinical experiences are needed for assessing the use of R in obstetric anesthesia. R causes either a reduction in the MAC of volatile anesthetics or a decrease in propofol requirements but it cannot be used as a sole anesthetic agent. R can be utilized to facilitate tracheal intubation without using muscle relaxants, to manage analgesia and sedation also in association with midazolam and/or propofol, furthermore as analgesic agent for monitored anesthesia care, for the critical patient in ICU and for the postoperative analgesia if a proper analgesic strategy had not been planned.