Low-flow anesthesia provides benefits of ecologic advantages, reduction of pollution of operating room, increased economy and prevention of airway dessication. It is worthy to gain popularity of application. In this review article, certain aspects of low-flow anesthesia are included: 1) how to avoid hypoxemia, 2) how to prevent carbon dioxide retention, 3) how to use Lin's method in calculating the metered concentration of inhalational anesthetics during maintenance period, 4) how the time constant to affect the time to surgical level of anesthesia, and 5) the indications of low-flow anesthesia for surgery. Finally, clinical experience in low-flow anesthesia will be discussed in terms of halothane, enflurane or isoflurane with or without nitrous oxide.