BACKGREOUND: The aim of this study was to compare the respiratory mechanics between young and elderly during enflurane anesthesia using flow-interruption technique. METHODS: Fourteen patients were divided into 2 groups; for young aged group (Group Y)(24.9 4.9 years) and old aged group (Group O)(73.4 5.6 years). After anesthetic induction, endotracheal intubation was performed with Univent tube, and then tracheal pressure was measured at the distal end of the tube. 1.5 vol% of enflurane and 0.15 mg/kg of vecuronium were administered to maintain anesthesia. IMV (intermittent mandatory ventilation) was applied with Siemens Servo 900C ventilator and anesthetic gases were supplied via low pressure inlet of the ventilator. Tidal volume (10 ml/kg) was fixed during measurements for each patient. After stabilization of vital signs, respiratory parameters were measured before surgery. End-inspiratory occlusion was applied at least 3 seconds. Pressure, flow and volume were monitored and recorded with Bicore CP100 pulmonary monitor. The data were transfered to a PC and analyzed by a processing software. Total respiratory (Rrs), airway (Raw) and tissue (Rve) resistances, and dynamic (Cdyn) and static (Csta) compliances were calculated. Mann-Whitney U test was used for statistical analysis. RESULTS: There were no statistically significant differences for the Cdyn and Csta values between the two groups. But the values of Rrs, Raw and Rve were higher in the Group O than the Group Y. CONCLUSION: During enflurane anesthesia, the values of Rrs, Raw and Rve were higher in the Group O than the Group Y. To elucidate the exact causes of the above results, further studies are needed.