An anesthetic delivery system for use in conjunction with an anesthetic return system for reutilizing anesthetic exhaled by a subject, the system including a measurement system operatively connected to a breathing circuit for continuously measuring at least one flow parameter and anesthetic content of a gas stream reaching the subject and a control system for receiving input from the measurement system and controlling the amount of anesthetic entering the system, the control system including an input device for inputting a setting that corresponds to a desired amount of anesthetic in the gas stream reaching the subject, and utilizing a control algorithm for controlling the amount of anesthetic entering the system based on said desired amount of anesthetic, and flow and anesthetic content parameters as determined by the measurement system, such that the control algorithm is adapted to supplement anesthetic already in gas stream flowing to the subject to attain a level of anesthetic reaching the subject that correspond to the desired amount set via the input device.