We studied the effects of insufflation gas and pressure on the adhesion, growth, apoptosis and necrosis of transitional cell carcinoma (TCC) in an in vitro model. Tumor adhesion and cell growth of AY-27 rat TCC was measured after 3-hour incubation with CO 2 , N 2 and He insufflation at different pressures (0, 10 and 15 mm Hg) in vitro. The effects of these gases on the rate of tumor cell apoptosis and necrosis were compared. In vitro the tumor adhesion rate was lowest with CO 2 and highest with N 2 . Higher gas pressures resulted in decreased adhesion rates for CO 2 and He but increased adhesion rates for N 2 . N 2 enhanced tumor cell proliferation at all pressures studied. He and CO 2 resulted in an initial increase in cell proliferation in the first 24 hours, followed by a decrease in tumor growth. Extracellular medium turned acidic in CO 2 (pH 6.27 to 6.39) but basic in N 2 and He (pH 8.39 to 8.84). At all insufflation pressures studied apoptosis and necrosis rates were increased in the first 24 hours, followed by a decrease for CO 2 and N 2 . He resulted in increasing apoptosis and necrosis throughout the study period. The type of gas and insufflation pressure affects cell adhesion and tumor growth. There was a significant increase in tumor adhesion and proliferation with N 2 insufflation compared with CO 2 and He at 0 to 15 mm Hg pressures. CO 2 demonstrated the greatest decrease in TCC adhesion and proliferation at 15 mm Hg pressure. Apoptosis and necrosis were highest for He compared with the other gases.