We have studied 14 female patients undergoing elective laparoscopy under general anaesthesia with peritoneal insufflation of carbon dioxide in order to examine changes in physiological deadspace (VDphys), arterial to end-tidal carbon dioxide partial pressure difference (PaCO2-PE' CO2) and PaCO2. VCO2 increased after insufflation of carbon dioxide with a mean (SD) maximum increase of 32 (28)% compared with the preinsufflation value. PaCO2 increased also, with a mean (SD) maximum increase of 0.6 (0.58) kPa immediately before carbon dioxide deflation. VDphys and (PaCO2-PE' CO2) increased during laparoscopy, but this was not significant (P greater than 0.05).