Fasting and postprandial gastric acid secretion and gastrin were determined in Heidenhain pouch dogs before (C) and after (R) massive enterectomy (five dogs) and after additional proximal gastric vagotomy (PGV) in three dogs. Basal acid output was unchanged (C = 7 +/- 2 microneq/hour; R = 11 +/- 4 microneq/hour), but postprandially the hourly (third through eighth hour) and cumulative acid outputs (C = 3.6 +/- 0.3 mEq/8 hour; R = 7.2 +/- 0.4 MEq/8 hour) were significantly increased by resection (P less than 0.001). Similarly, fasting gastrin was unaltered by resection (C = 41 +/- 2 pg/ml; R = 46 +/- 8 pg/ml), whereas hourly gastrin concentrations significantly (P less than 0.05) exceeded control values. Increased gastrin correlated linearly (P less than 0.02) with increased acid output. After PGV, basal acid levels remained unchanged (R = 4 +/- 2 micronEq/hour; PGV = 9 +/- 4 micronEq/hour), but postprandial acid output significantly exceeded prevagotomy values at all time periods (P less than 0.05). Cumulative acid output also was increased (R = 6.8 +/- 0.6 MEq/8 hour; PGV = 11.2 +/- 0.6 mEq/8 hour; P less than 0.001). Serum gastrin, however, remained unchanged. Hypersecretion of acid from Heidenhain pouches after massive enterectomy is increased further by PGV without a concomitant increase in serum gastrin.