Levels of digestive enzymes were analyzed in water snakes following artificial feeding. A prominent increase of total proteolytic activity in the stomach was evident after feeding with a casein solution or after the snake was offered a fish (9- and 6-fold that of the fasting level, respectively). The activity following feeding with starch was much lower. Increased levels of chymotrypsin(ogen) as well as of amylase were evident in the pancreas 1 day after feeding the snake with fish. A specific induction of increased level of chymotrypsin in the pancreas of adult snakes was achieved by feeding with casein (12-fold that of the fasting level). In the group fed with starch, the chymotrypsin level dropped, while a 3-fold increase of amylase was evident. In newborn snakes, fed for the first time, casein induced a dramatic increase in the level of chymotrypsin in the pancreas (58 times the fasting level); feeding with starch induced an approximate 2-fold increase of chymotrypsin. Histological examination of the pancreas 1 day following casein feeding showed acinar cells loaded with zymogen granules. In starved animals and in snakes fed with starch, a much lower concentration of zymogen granules was observed. The pancreas of the snake may, thus, be most suitable for studying the specific induction of synthesis of digestive enzymes.