We investigated the role of low-doses of bombesin in the regulation of exocrine secretion in the pancreas of the conscious pig. In ten growing castrated male Large White pigs, bombesin was infused intravenously for 1 h at doses of 0 to 500 pmol/kg/h under a stimulation of secretin (36 pmol/kg/h). In six pigs, bombesin (50 pmol/kg/h) was administered alone for 2 h and its effect on pancreatic secretion was compared to that of an infusion of secretin. The pancreatic juice and the blood were collected at 15-min intervals for use in assays of protein in the juice and gastrin in the plasma. When bombesin was infused alone or in combination with secretin, the volume secreted was not altered. The protein output was not altered by secretin, but was increased by the infusion of bombesin, in a dose-dependent manner, reaching a plateau at 250 pmol/kg/h. The plasma gastrin levels were increased by bombesin, starting with the 50 pmol/kg/h dose. This effect was maximal at a dose of 100 pmol/kg/h. The levels remained below those measured after a standard meal, demonstrating that the effect of bombesin on the studied parameters is of physiological significance.