Hemodynamic changes caused by a pneumoperitoneum have been studied in healthy animals. In an experimental model in pigs with impaired pulmonary function we wandted to examine the hemodynamic changes during laparoscopic nephrectomy. 13 pigs were anesthetizid with azaperon/ketamine and ventilated with 67% nitrous oxide in oxygen. By i.v. injection of starch microsphers a capillary pulmonary embolism was induced. After embolisation 3 animals served as untreated controls (group 1), 5 animals underwent an open nephrectomy (group 2), and 5 underwent a laparoscopic nephrectomy (group 3). Group 3 developed a significant CO2 retention with a consecutive acidosis. There was a significant increase of cardiac output volume from 3.6 1/min. (+/- 0.62) to 4.5 1/min. (+/- 0.47) in Group 3, whereas group 2 showed a significant decrease from 3.6 1 /min. (+/- 0.41) to 2.1 1/min. (+/- 1.2). The laparoscopic approach was in our model associated with a significant increase of cardiac output, whereas open surgery was combined with a significant decrease.