The aim of this study was to assess gastric anatomy, motility, and emptying after vertical banded gastroplasty and to correlate the anatomic and physiologic results with clinical outcome. Eleven patients were studied at least 7 mo after operation, by which time they had lost 31% +/- 4% (mean +/- SEM) of their excess body weight. Stomal diameter, volume, and distensibility of the proximal gastric pouch were determined by a balloon distention technique. Gastric emptying was monitored scintigraphically both with and without distention of the proximal pouch. Stomal diameters ranged from 10 to 15 mm (mean +/- SEM = 11 +/- 1 mm), and pouch capacity ranged from 20 to 150 ml (76 +/- 9 ml). Mean intrapouch pressure was 13 mmHg before distention, increased to 22 mmHg with distention to half-maximal capacity, and then changed little with further distention to maximum capacity. Near maximal pouch distention during gastric emptying of a 300-ml test meal decreased antral contractile activity and speeded the initial rate of emptying (t25 with distention = 14 +/- 3 min vs. 24 +/- 3 min without distention, p less than 0.03), but did not alter the later rate of emptying. No clear-cut relationship was present between weight loss and stomal diameter, pouch volume, or gastric emptying. The conclusion was that distention of the proximal gastric pouch created by vertical banded gastroplasty inhibited antral contractions and increased the initial rate of gastric emptying, but no clear-cut correlation was found in this cohort between weight loss after the operation and stomal diameter, pouch size, and gastric emptying.