During the laparoscopic cholecystectomy, the ventilatory and hemodynamic changes could occur due to the peritoneal insufflation of CO2 as well as the position change. Various sults of the relationship between arterial and end-tidal PCO2 in different conditions have been reported. The authars studied to determine how closely end-tidal PCO2 reflects arterial PCO2 before, during, and after laparoscopic cholecystectomy. Peak inspiratory airway pressures, arterial blood pressures and heart rates were also measured simultaneously. Peritoneal insufflation of CO2 resulted in significant increase in peak inspiratory airway pressure and arterial blood pressure, but there were no significant changes in heart rates. Arterial and end-tidal PCO2 increased during laproscopy and, although there was no statistical significance in P(a-ET)CO2, P(a-ET)CO2 increased during laparoscopy and retumed to perinsufflation level after deflation of CO2. There was positive correlation between arterial and end-tidal PCO2 before CO2 insufflation, 10 minutes after CO2 insufflation and 10 minutes after deflation of CO2. However there was no correlation at 30 and 50 minutes after CO2 insufflation. These results suggested that the arterial PCO2 could not reflect end-tidal PCO2 exactly, and intermittent arterial blood gas studies should be warranted during laparoscopic cholecystectomy.