Although there are many studies evaluating the effect of elevated gastric pressure in total wrap and partial anterior and posterior wrap fundoplications, there are no ex vivo manometric studies evaluating the contribution of elevated gastric pressure to prevention of gastroesophageal reflux (GER) in Collis and uncut Collis procedures without fundoplication. An experimental study has been designed to determine the contribution of elevated intragastric pressure in the absence of in vivo anatomic and functional factors to the prevention of GER in Collis and uncut Collis without fundoplication procedures. The study was conducted on adult male New Zealand rabbits' esophagus and stomachs. The stomachs were divided into four groups: total wrap fundoplication group, partial wrap anterior fundoplication group, Collis without fundoplication group, and uncut Collis without fundoplication group. The minimum intragastric pressure (MIP) causing GER of each stomach before and after the procedure were measured with a two-way catheter introduced through the pylorus. The MIP values causing GER of the total wrap and partial anterior wrap fundoplication groups were found to be significantly higher compared with the basal intragastric pressures (P < 0.01). The MIP values causing GER of the Collis and uncut Collis without fundoplication groups were not significantly different compared with basal intragastric pressures (P > 0.05). The elevated gastric pressure is found to be insufficient to prevent GER in Collis and uncut Collis without fundoplication procedures. The efficacy of these procedures in preventing GER seems to be related to the anatomic and functional factors affecting in vivo circumstances.