Among the recent developments in the field of transdermal drug delivery, iontophoresis has emerged as a very promising tool for this purpose. Various studies have been performed on drug delivery through the skin using electric current. Iontophoresis has thereby been found to be effective in particular in transdermal protein and peptide drug delivery. This article reviews the principle, potential benefits, and applications of drug delivery based on iontophoresis. It focuses furthermore on current research and future trends in the field of iontophoretic drug delivery.