Target controlled infusion (TCI) is an infusion system which allows the anesthetist to select the target blood concentration required for a particular effect and then to control the depth of anaesthesia by adjusting the requested target concentration, which includes the instantaneous calculation of the infusion rate necessary to obtain and maintain a given therapeutic blood concentration of drug based on average pharmacokinetic parameters. We can apply this concept of infusion system not only to anesthetics but also to any kinds of intravenous drug infusion including antibiotics in the future.