Abstract: In a method and an apparatus for determining the position of an esophageal catheter that is inserted into the esophagus of a patient, the catheter having a number of electrodes, muscular activity of the diaphragm is stimulated by applying a stimulus signal that produces a myoelectrical signal in the diaphragm having a well-defined peak at a specific point in time. The myoelectrical signal is detected by respective pairs of electrodes of said catheter, and the electrode pair or pairs that detected the signal having the highest amplitude at the specific point in time is identified. If this electrode pair or these electrode pairs that detected the signal with highest amplitude are not located approximately at the middle of the catheter, an indication is emitted that the position of the catheter should be adjusted.