The aim of this study was to elaborate on a computerized microthermistor technique for indirect measurement of esophageal blood flow and to investigate if any changes in circulation could be found in patients who are provoked by esophageal acid perfusion of their acid-sensitive mucosa. A thermistor was mounted in a plastic catheter and placed in the esophagus 11 cm above the lower esophageal sphincter. The signal from the thermistor was transmitted to a personal computer. A 15~ water bolus was injected into the catheter in order to cool the esophageal wall at the catheter side hole 1 cm above the thermistor. The reliability of the thermistor test was examined by repeating it in 29 patients. No statistical difference between the two test occasions was found. Twenty-five patients were provoked with an acid perfusion test, 14 of whom had a positive reaction with heartburn. Patients with a positive acid perfusion test had a shorter rewarming time before as well as after provocation than patients with a negative acid perfusion test. It is concluded that this thermistor technique is well suited for measuring intraluminal rewarming rate as an indirect sign of changes in esophageal blood flow. Furthermore, the results indicate that blood supply of the esophageal wall is increased in patients with a positive acid perfusion test.