Tension pneumoperitoneum may force gas into a small injured vessel if the opening is kept patent by surrounding tissues. However, the amount of carbon dioxide (CO2) that penetrates through injured or noninjured peritoneum has not been systematically determined. In 25 patients undergoing elective laparoscopic ultrasonography and cholecystectomy, CO2 output (JOURNAL/jcmc/04.02/00115725-199814030-00004/OV0312/v/2017-11-08T004958Z/r/image-pngCO2) and O2 uptake (JOURNAL/jcmc/04.02/00115725-199814030-00004/OV0312/v/2017-11-08T004958Z/r/image-pngO2) were measured at baseline and during anesthesia, pneumoperitoneum, laparoscopic surgical procedure (Surgery), and after hemostasis of the surgical field (Postsurgery). Before anesthesia,JOURNAL/jcmc/04.02/00115725-199814030-00004/OV0312/v/2017-11-08T004958Z/r/image-pngCO2/BSA and JOURNAL/jcmc/04.02/00115725-199814030-00004/OV0312/v/2017-11-08T004958Z/r/image-pngO2/BSA were 97.7 ± 11.3 and 116.0 ± 10.0 ml·min−1·m−2, respectively. During anesthesia, they fell to 72.3 ± 6.0 and 89.8 ± 7.6 ml·min−1·m−2 (p < 0.05). VCO2/BSA increased to 96.0 ± 11.1 at pneumoperitoneum (p < 0.05) and increased further to 126.1 ± 11.0 ml·min−1·m−2 at Surgery. It fell to 111.7 ± 10.9 ml·min−1·m−2 Postsurgery. JOURNAL/jcmc/04.02/00115725-199814030-00004/OV0312/v/2017-11-08T004958Z/r/image-pngO2/BSA remained unchanged during pneumoperitoneum. Minute volume increased from 2.24 ± 0.20 in anesthesia to 2.89 ± 0.25, 4.01 ± 0.32, and 3.46 ± 0.28 L·min−1·m−2 during pneumoperitoneum, Surgery, and Postsurgery, respectively, to maintain PaCO2. We conclude that the amount of CO2 absorbed following pneumoperitoneum prior to surgery is lower than that during Surgery or Postsurgery. The amount of CO2 absorbed through the surgical field was 2.3 times higher than that through the nonsurgical field, while that from the peritoneum after hemostasis of surgical field was 1.6 times higher.