Fentanyl is a highly potent, short acting synthetic analgesic indicated as a preanesthetic medication. It is available for intravenous injection, as a transdermal patch and a lozenge dosage form. Fentanyl displays a large apparent volume of distribution, short plasma half life and extensive biotransformation. It is a popular drug of abuse among health care professionals. Diversion of pharmaceutical fentanyl preparations, as well as the availability of illicitly synthesized potent and highly toxic fentanyl analogs have resulted in numerous overdose deaths. Analysis of fentanyl and fentanyl analogs requires highly selective and sensitive methodologies. This review is intended as a quick reference source for clinical and analytical toxicologists.