The authors investigated the kinetic pattern of exocrine pancreatic secretion on 60 anesthetized dogs. The kinetic pattern of juice and enzyme secretion follows the same mathematical rules. The curves obtained are governed by an exponential function. Kinetic data of pancreatic secretion make it possible to estimate the half-life time of secretín and cholecystokinin/pancreozymin (CCK/PZ) by an indirect method. The half-life time of secretin and CCK/PZ is defined as the period of time in which the activity of the hormones -measured on the parameter of pancreatic secretion (flow rate, rate of enzyme secretion) – decreases to one half. The half-life time of the two hormones is not constant. The mean half-life time of secretin is approximately 3.2 min, that of CCK/PZ 1.8 m