The secretion of pancreatic juice was studied in cattle from the first days of life to the start of rumination and in adult cows. Synchronized periodic oscillations of pancreatic secretion in phase with the duodenal migrating motor complex were observed in calves from 2^nd-3^rd day of life. These pancreatic oscillations developed with the maturation of the gastrointestinal tract. In adult cattle, pancreatic secretion was relatively stable and essentially did not respond to feeding. However, manipulation of the diet effectively changed daily exocrine secretion, and it is hypothesized that the insulo-acinar axis may be important in this respect. The importance of the vagal nerves, gastrointestinal regulatory peptides, and duodenal contents in the regulation of pancreatic secretion in young and adult cattle is discussed. Some gastrointestinal regulatory peptides affect the pancreas indirectly from the site of their release, i.e., the proximal duodenum in preruminant calves. Vagal extrinsic innervation appears to play a critical permissive role in the effect of gastrointestinal regulatory peptides on the exocrine pancreas.