Changes in specific activity levels of disaccharidases in the intestine and of phosphatases in liver and intestine were studied during development of the chick embryo and chick. A diversity of developmental patterns were observed among the various enzymes. However, many of the intestinal enzyme activities showed marked increases about the time of hatching, and some declined rapidly from transient peaks shortly after hatching. Most of the hepatic enzyme activities were present at relatively high levels in the embryo and showed modest changes from these levels about the time of hatching. Hydrocortisone administration to embryos evoked premature increases of a number of intestinal enzymes, but resulted in substantial reduction of several hepatic enzyme activities. The different patterns of enzymic differentiation in the two tissues are discussed.