Abstract.The effects of repeated intravenous calcium administration on pancreatic juice secretion were investigated in four Thomas fistula dogs. During stimulation by 1.0 U kg‐1h‐1GIH secretin, three Ca doses were administered: 2, 4 and 8 μmol kg‐1min‐1during 1 h, saline being used in control tests; one dose only was tested per day. It was found that Ca administration induced both acute and long‐lasting effects. Acute effects were characterized by an increased response to secretin stimulation. Fluid, HCO3‐, protein and Ca outputs increased significantly in a dose‐dependent manner, the increase of protein output being the most dramatic. Long‐lasting effects, until now unrecognized, were characterized by a progressive increase of protein secretion during the first hour of secretin stimulation. This increase kept going during the 3 months of repeated calcium injections. Although protein plugs were observed in the juice, sometimes stopping the flow of juice, no pancreatic lesion was found. A second protocol showed that, after discontinuing calcium injections, the long‐lasting effects decreased progressively, but protein hypersecretion was still significant 3.5 months later. The importance of these findings regarding chronic pancreatitis due to hyperparathyro