SUMMARY Measurements of cardiac output, mean arterial pressure, central venous pressure, and heart rate were made in seven patients undergoing laparoscopy. Measurements were made before and after insufflation of the peritoneum with carbon dioxide, and again after intravenous injection of oxprenolol 2 mg. No significant change in cardiac output followed peritoneal insufflation, but there was a significant increase in mean arterial pressure, central venous pressure, and heart rate. Following the administration of oxprenolol, cardiac output, mean arterial pressure, and heart rate all fell, and central venous pressure rose further. Only the change in heart rate was statistically significant. Blood gas analysis in five patients showed a rise in Pac02 and fall in pH after insufflation with carbon dioxide. The implications of these findings are discussed.