Abstract： AIM:To determine if the observed paracellular sucrose leak in Barrett's esophagus patients is due to their proton pump inhibitor (PPI) use.METHODS:The in vivo sucrose permeability test was administered to healthy controls,to Barrett's patients and to non-Barrett's patients on continuous PPI therapy.Degree of leak was tested for correlation with presence of Barrett's,use of PPIs,and length of Barrett's segment and duration of PPI use.RESULTS:Barrett's patients manifested a near 3-fold greater,upper gastrointestinal sucrose leak than healthy controls.A decrease of sucrose leak was observed in Barrett's patients who ceased PPI use for 7 d.Although initial introduction of PPI use (in a PPI-nafve population) results in dramatic increase in sucrose leak,long-term,continuous PPI use manifested a slow spontaneous decline in leak.The sucrose leak observed in Barrett's patients showed no correlation to the amount of Barrett's tissue present in the esophagus.CONCLUSION:Although future research is needed to determine the degree of paracellular leak in actual Barrett's mucosa,the relatively high degree of leak observed with in vivo sucrose permeability measurement of Barrett's patients reflects their PPI use and not their Barrett's tissue per se.