Objective: The aim was to determine the influence of the pneumoperitoneum at 10, 13, and 16 mm Hg on thromboelastograph (TEG) in laparoscopic cholecystectomy. METHODS: Sixty patients were randomly allocated to 3 groups. The abdomen was insufflated with carbon dioxide to 10 mm Hg (group 1), 13 mm Hg (group 2), and 16 mm Hg (group 3) intra-abdominal pressures. We evaluated changes in the TEG values [reaction time (R), maximum amplitude (MA), α-angle, K time] preoperatively, intraoperatively, and postoperatively. Results: In the postoperative 24th hour, the R-value was significantly lower in group 3 than that in group 1 and group 2 (P<0.05). We found increased values of MA intraoperative 30th minute and postoperative 24th hour in group 3 with respect to group 1 (P<0.05) and postoperative 24th hour, and the MA value in group 3 was significantly higher than those of group 2 (P<0.05). In group 3, the α-angle was significantly higher than that of group 1 and group 2 at intraoperative 30th minute and postoperative 24th hour (P<0.05). In postoperative 24th hour, the K-value was significantly lower in group 3 than in group 2 and group 1 (P<0.05). Conclusions: Laparoscopy with pneumoperitoneum at pressures of 10 and 13 mm Hg did not alter the TEG values and low intra-abdominal pressure must be used for peritoneal insufflation. © 2011 by Lippincott Williams & Wilkins.