Truncal vagotomy (TV) is known to increase the feeding stimulated acid output of Heidenhain pouches. A series of experiments were performed in dogs to see if proximal gastric vagotomy (PGV) also had this effect. Dogs were prepared with gastric fistulas (GF) and Heidenhain pouches (HP). Gastric function testing included three categories of tests: (1) serum gastrin determinations and Heidenhain pouch acid secretion after feeding, (2) gastric emptying and simultaneous Heidenhain pouch acid secretion, and (3) gastric and Heidenhain pouch acid secretion and serum gastrin levels after insulin. Compelte testing consisting of two control and two post-PGV tests was accomplished in five dogs in each category. Insulin testing confirmed that an adequate PGV was performed because GF peak acid output in response to 0.5 U/kg insulin IV was reduced 88% by PGV (p less than .01). In response to two separate meals peak acid output (PAO) from the HP's was not increased significantly after PGV: Meal I pre-PGV 450 +/- 112 vs post-PGV 400 +/- 99 muEq/15 min; Meal II pre-PGV 256 +/- 62 vs post-PGV 304 +/- 150 muEq/15 min. This finding may represent an important physiologic difference between PGV and truncal vagotomy.