Knowledge of the competence of the oesophago-gastric junction (OGJ) is fundamental to the understanding of gastro-oesophageal reflux disease (GORD), a disorder with a high incidence among the general population. A catheter with a bag 9.5 cms long mounted towards the distal end was swallowed by three volunteers. Using manometry readings and the point of respiratory inversion as a guide the probe was placed in the OGJ. The bag was distended with saline at a fixed rate volume before and after the administration of butylscopolamine to block cholinergic-mediated contractile smooth muscle activity. Using impedance planimetry three cross-sectional areas (CSA) measurements were made between three pairs of electrodes with 4 mm between each electrode on the catheter placed inside the ballon. Using the law of Laplace, CSA and pressure data could be calculated to give wall tension. Tension rose in all volunteers as the radius increased and it was higher towards the proximal end of the OGJ indicating that this measurement can be used to show the distensibility of the OGJ at different degrees of opening. This technique could be useful in identifying changes in the competence of the lower oesophageal sphincter in some patients with GORD.