BACKGROUND: The anesthesia machine PhysioFlex was especially constructed to deliver anesthetics in a closed circuit system. In this anesthesia machine the concentrations of the respiratory gases and the gas volume in the circle system are automatically controlled by a feedback mechanism. The aim of this study is to introduce 1,132 patients who have received general anesthesia in a closed circuit system using PhysioFlex, and to calculate the real consumed amount of oxygen and nitrous oxide, and to describe the advantages and disadvantages of PhysioFlex for clinical uses. METHOD: The author used a PhysioFlex in cases of 1,132 various surgical interventions. After induction with thiopentone and suxamethonium, general anesthesia was maintained with nitrous oxide in 50% oxygen and enflurane (or isoflurane, halothane) and supplemented with nalbuphine and pancuronium. These cases were analyzed by their sex, age, height, weight, method of airway maintenance during general anesthesia, operation position, anesthesia time, and arterial blood gases by review of anesthesia records. Average minute-consumed amount of oxygen and nitrous oxide was calculated by recording every 30 seconds throughout the anesthesia procedures except preoxygenation and flush periods. The advantages and disadvantages of PhysioFlex were described on the base of the author's clinical experience. RESULTS: The anesthetic technique of the closed circuit system by PhysioFlex could be used adequately for any surgical procedures. In this system consumed amounts of oxygen and nitrous oxide were 179.72+/-2.48 ml/min and 88.49+/-2.78 ml/min respectively. The author found out several advantages and few disadvantages of PhysioFlex for its clinical uses. CONCLUSIONS: Closed circuit system of PhysioFlex anesthesia machine offer numerous advantages such as reduction of gas consumption, low cost, less pollution in both the operating theater and the environment, increase in inspired gas humidity, easy handling of machine, and excellent respiratory alarm systems.