["Pathophysiological mechanisms associated with neoplastic progression in patients with short-segment Barrett's oesophagus (SSBO), who represent the vast majority of the Barrett population, have not been defined.", 'To evaluate pathophysiological characteristics of patients with SSBO and dysplasia detected at 3-year surveillance endoscopy (incident dysplasia).', 'Patients with SSBO underwent impedance-pH monitoring during heartburn-suppressing PPI therapy. Fifteen patients (12 males, median age 62 years) with incident dysplasia and 50 patients (43 males, median age 59 years) without dysplasia were compared. Impedance-pH parameters, including chemical clearance assessed by the post-reflux swallow-induced peristaltic wave (PSPW) index, were evaluated.', 'All patients declared persisting heartburn suppression on maintenance PPI therapy at 3-year follow-up, 58/65 (89%) with standard dosages. The median gastric and oesophageal acid exposure time (GAET and OAET) did not differ between patients with and without incident dysplasia at the time of surveillance (36% and 0.6% vs. 33% and 0.5%) or index endoscopy (33% and 0.3% vs. 41% and 0.5%) (P > 0.05). Contrastingly, the median PSPW index was significantly lower in patients with than in patients without incident dysplasia at the time of surveillance (15%, vs. 32%) and index endoscopy (12% vs. 30%) (P = 0.001). The PSPW index, the GAET and the OAET did not vary over time (P > 0.05). A PSPW index <26% was predictive of incident dysplasia with a 75% accuracy.'] Is neoplastic progression in short-segment Barrett 's oesophagus associated with impairment of chemical clearance , but not inadequate acid suppression by proton pump inhibitor therapy?