Opioid administration by patient-controlled analgesia (PCA) is the standard therapy for acute postoperative pain. Despite its utility in this setting, limitations of this modality do exist. Consequently, noninvasive PCA systems, including an iontophoretic transdermal system (ITS) with fentanyl hydrochloride, are under development to circumvent many of these limitations. This preprogrammed, self-contained, compact, needle-free system provides pain control superior to that of placebo and comparable to morphine PCA in the first 24 hours after major surgical procedures. The objectives of this article are to describe the method of transdermal iontophoretic medication administration and to review the literature pertaining to the fentanyl ITS.