Background: Numerous experimental and clinical investigations indicate that the mononuclear phagocyte system (MPS) has a relevant function in terms of physiological defense against tumor metastasis and bacterial infection. Consequently, a point of major interest is the influence of surgical techniques on the MPS function. Method: The model investigation examines the phagocytosis activity of the rat's MPS during conventional fundoplication (group 1, n ‫ס‬ 10), laparoscopic fundoplication using a pneumoperitoneum (group 2, n ‫ס‬ 10), and gasless laparoscopic fundoplication (group 3, n ‫ס‬ 10). The MPS function is evaluated by an intravascular carbon clearance test (G. Biozzi). Results: The fastest carbon elimination half-life was found in group 3. By way of contrast, there was a significant increase of carbon half-life in group 2 (p < 0.005). Even group 1 caused less MPS depression (p < 0.1) than group 2. Conclusion: Gasless laparoscopic procedures have a favorable effect on phagocytosis activity. The CO 2 pneumoperitoneum seems to be the main reason for a decreased antigen elimination in laparoscopic treatments.