Introduction: The aim of this study is to determine the relationship of hydrochloric acid secretion in gastric pouch (GP), an orthotopic neobladder using a stomach segment, to gastrin. Material and Method: Pentagastrin (PG) stimulation test (PGST) was applied in 10 patients who had had GP surgery 5-70 months ago, and their urinary pH changes in the next 2 h were observed. Results: Significant pH decreases (from 6.6 +/- 0.6 to 2.9 +/- 1.0 in the mean) 30-75 min after injection of PG, demonstrating gastrin-triggered acid secretion in GP were observed in all patients. The pH values were normalized in 2 h (6.6 +/- 1.0 in the mean). Conclusion: In PGST, urinary pH decreases, demonstrating the close relationship between gastrin release and acid secretion in the GP. Inhibition of gastrin by any means may be useful in keeping the urinary pH on physiological levels. Copyright (C) 2003 S. Karger AG, Basel.