Forty male rats weighing 150 g were operated on with gastrectomy with esophagoduodenostomy, antrectomy, fundectomy, or bilateral truncal vagotomy with pyloroplasty. Unoperated rats served as controls. The rats were freely fed, but not pair-fed, until sacrifice by exsanguination after 8 weeks. The pancreas was excised, weighed, and analyzed for contents of water, protein, amylase, and DNA. Basal levels of serum gastrin and plasma cholecystokinin (CCK) were only measured at sacrifice. Eight weeks after the operation, gastrectomized and antrectomized rats had lowered serum gastrin concentrations, while fundectomized and vagotomized rats had increased concentrations as compared with control rats. The concentration of plasma CCK was increased in fundectomized rats only. The operated rats had a lower body weight than the controls. The pancreatic wet weight relative to the body weight was increased after gastrectomy and vagotomy, but decreased after antrectomy. The protein content was lowered after antrectomy, but the content relative to the body weight was increased after gastrectomy and vagotomy. Antrectomy decreased the DNA content, while the other operative procedures were without similar effect. The pancreas was atrophic after antrectomy with a decreased DNA content, whereas gastrectomy evoked a slight hypertrophy, although both procedures induced hypogastrinemia. Fundectomy did not evoke any changes in the pancreas, whereas vagotomy increased the amylase content. Neither the concentration of gastrin in serum nor the concentration of CCK in plasma correlated with any of the changes in the pancreatic parameters studied. Thus, gastric surgery in the rat influenced the pancreatic integrity, but the observed changes were unrelated to basal levels of serum gastrin and plasma CCK.