Introduction: The proximal cardia region of the stomach has a high incidence of inflammation, metaplasia and neoplasia. It demonstrates less acid buffering following meals than the more distal stomach. Novel high definition pHmetry was employed to investigate acidity at the cardia under fasting conditions and in response to a meal. Methods: 15 healthy subjects were studied. A custom-made 12-electrode pH catheter was clipped at the squamocolumnar junction with four electrodes recording proximal to and eight distal to the squamocolumnar junction. The most distal pH electrode was located at the catheter tip, and nine electrodes in the region of the squamocolumnar junction were 11 mm apart. Results: The electrode situated in the cardia 5.5 mm distal to the squamocolumnar junction differed from all other intragastric electrodes during fasting in recording minimal acidity (pH Conclusion: Whereas the rest of the stomach shows a marked fall in acidity on ingesting a meal, the cardia paradoxically increases in acidity to become the most acidic region throughout the postprandial period.