Glucagon release from the gastric fundus and pancreas were compared in normal dogs by measuring glucagon in plasma from a major gastroepiploic vein, the superior pancreaticoduodenal vein, and the inferior vena cava. In 32 dogs in the basal state, gastric vein glucagon averaged 97 +/- 40 pg/ml, not significantly different from the 93 +/- 41 pg/ml level in the vena cava. Pancreaticoduodenal vein glucagon averaged 250 +/- 32 pg/ml (P less than 0.001). Intravenous arginine infused in four dogs caused a rise in mean gastric vein glucagon to 210 +/- 33 pg/ml within 3 min, and glucagon remained between 53 and 98 pg/ml above the vena caval level thereafter. In the gastric vein, the rise in glucagon was significantly greater than in the vena cava at 3, 5, and 10 min (P less than 0.05), but was far less than in the pancreaticoduodenal vein where glucagon rose to 1,295 +/- 379 pg/ml at 1.5 min. Evidence of modest gastric glucagon release was observed after the intragastric instillation of arginine, but not during insulin or phloridzin-induced hypoglycemia. It was concluded that in normal dogs under the circumstances studied, the gastric fundus is not a major source of circulating glucagon.