The feasibility of iontophoresis on the transdermal delivery of captopril was studied.Iontophoresis was employed for enhancing transdermal transport of captopril through rat skin in vitro and in vivo.It was demonstrated that the iontophoresis-induced flux of captopril was affected by various factors such as pH, ionic concentration, and the concentration of captopril in donor compartments as well as the applied electric current intensity. Electric current could induce several-fold increase in captopril flux with hydrogel. Skin permeation study in vivo in rats demonstrated that iontophoresis could effectively promote the transdermal transport of captopril without significant skin irritation. Captopril concentration in plasma reached plateau (approximately 0.9 microgram/mL) at 1 h after current application and was maintained at the same level during the experiment. On the contrary, captopril could not be detected in plasma when the current was not applied. No obvious skin irritation was observed after 9-h continuous iontophoresis.Transdermal delivery of captopril can be effectively improved by iontopophoresis.