New manometric techniques in for examining the lower oesophageal sphincter (LOS) were applied an investigation of the oesophago-gastric junction after partial gastric resection. Pressure and blood gastrin data are reported for eight cases examined before and after surgery, under basal conditions and after stimulation with a protein meal. It was found that gastric resection leads to a decrease in LOS performance (43.6% fall in maximum pressure) and length (-33.3%). There is also a 93.5% decrease in the pressure response to a protein meal, and hence a predisposition to gastroesophageal reflux.