We studied the effect of esophageal inflammation on lower esophageal sphincter (LES) pressure in cats by measuring LES pressure and taking mucosal biopsies before and after the development of experimental esophagitis, as well as after a 3 1/2-week recovery period. Perfusion of the esophagus with 0.1 N HCl for either 1 hr or 1/2 hr per day for 4 days produced inflammatory changes by mucosal biopsy and was associated with a marked decline in LES pressure. Upon resolution of the inflammation, LES pressure returned to normal. Biopsies were normal in control groups which underwent either esophageal perfusion with distilled water or intragastric perfusion with acid, 1 hr per day for 4 days, and LES pressures in these groups remained unchanged from pre-perfusion values. These studies indicate that lower esophageal inflammation per se adversely affects LES pressure in cats, and that experimental esophagitis may be a useful model for the study of LES function and its relation to esophageal inflammation.