Abstract: An anesthesia machine output monitor (AMOM) which performs the functions of measuring the flow and composition of anesthesia gases delivered by the anesthesia machine, measuring on-line the amount of inhaled anesthetic used during a procedure requiring an anesthetic agent, measuring on-line the cost of inhaled anesthetic used during a procedure requiring an anesthetic agent, and integrating with an automated anesthesia recorder (AAR) to allow the recording of anesthetic gas flow rates and composition during a procedure and the cumulative cost of the anesthetic gases used during the procedure. The anesthesia gas flow rates and composition are measured using a modified infrared anesthetic gas analyzer that measures anesthetic gas composition and a pitot tube that is inserted in the common gas outlet of the anesthesia machine in order to measure the composition and flow rates of gases as they exit the anesthesia machine.