Amylase activity in several tissue and body fluid compartments in the rat changed markedly when the secretion of digestive enzyme was augmented over a 3-hr period with a cholinergic agonist. As a result of stimulation, the pancreas was depleted of about one-third of its amylase activity and accounted for only 75% of the amount recovered from the animal, compared to 92% in the fasted state. Despite the continuous augmented secretion of the enzyme into the small intestine, no increase in amylase activity was detected there at the end of 3 hr. On the other hand, amylase activity in plasma and extracellular fluid increased by about an order of magnitude and accounted for 13% of the total pool, compared to approximately 1% in the fasted state. Amylase activity in several solid tissues also increased, including a 50- to 100-fold increase in parotid gland and an almost 10-fold increase in submandibular gland and kidney. The potential sources of the increased amylase activity in blood, the endocrine secretion of the enzyme by the pancreas, and its absorption from the intestine are considered. Changes in the amylase content of various tissues appear to reflect increased uptake due to increased plasma levels.