Surgical trauma may be associated with enhanced tumor growth and establishment. The authors studied the effect of carbon dioxide (CO(2)) pneumoperitoneum versus laparotomy on tumor necrosis factor-alpha (TNFalpha), migration inhibitory factor (MIF) expression, and nuclear factor kappa B (NFkappaB) activity in human gastric cancer. Nude mice were inoculated intraperitoneally with human gastric cancer cells (MKN45). Then laparotomy, CO(2) pneumoperitoneum, and anesthesia alone were performed randomly. Tumor growth and associated TNFalpha and MIF expression and NFkappaB activity were determined. Total tumor weight, especially at the anterior abdominal wall, was higher after laparotomy than after CO(2) pneumoperitoneum (p < 0.05). The mRNA expression of TNFalpha was higher 24 and 48 h after laparotomy than after CO(2) pneumoperitoneum (p < 0.05 and p < 0.01, respectively). At all the examined time points, MIF mRNA expression also was higher after laparotomy than after CO(2) pneumoperitoneum (p < 0.05 until 1 week or p < 0.01 at 2 weeks). The NFkappaB protein was more activated after laparotomy than after CO(2) pneumoperitoneum 6 h subsequent to surgical procedures. After CO(2) pneumoperitoneum, tumors have less TNFalpha and MIF expression and less NFkappaB activity than after laparotomy. This may be associated with less tumor growth, supporting minimal invasive techniques in gastrointestinal oncologic surgery.