The underlying mechanism by which the reflux of gastric juice elicits oesophagitis remaind unclear. To investigate inflammatory response to HCI in tissue of esophagus and lower esophageal sphincter experimental esophagitis was elicited by perfusion of 0.1 N HCI in cats. There was no difference in phospholipase $A_2$ (PLA$_2$) activity of tissue between control and esophagitis. Myeloperoxidase activity in esophagitis was significantly greater than that of control. However histamine content in esophageal mucosa of esophagitis was significantly smaller than that of control. These finding suggest that inflammatory response to HCI in esophagitis is related to changes of myeloperoxidase activity and histamine rather than change of PLA$_2$ activity.