Equipment for administering gaseous anesthetic to a patient has at least one anesthetic reservoir serving as the originating source for anesthetic and a ventilator to which the gas is supplied from the reservoir, the ventilator being in communication with the breathing passages of a patient. To maintain the consumption of anesthetic gas as low as possible and to also assure that the patient is constantly ventilated with fresh anesthetic gas having a defined consumption, the exhalation gas from the patient is fed back to the originating anesthetic source via at least one filter in which predetermined gas components, such as water vapor and carbon dioxide are filtered out. The exhalation gas may be returned to the originating source either directly or through a compressor.