Changes in small intestinal morphology, in the indices of cellular development, and in the activities of some mucosal enzymes were examined in broilers from hatch through 14 d. In addition the effects of holding birds without access to feed for 36 h and of deutectomy were examined. Development of the intestine was rapid from 2 d after hatch although rates of development were different in duodenum, jejunum, and ileum. Villus volume in the duodenum reached a plateau after 7 d although it continued to increase in the jejunum and ileum. Enterocyte density changed little with age. Indices of tissue activity, ribosomal capacity, and cell size decreased with age but at differing rates at the three intestinal sites. Sucrase-maltase activity was low in the duodenum and highest in jejunum and ileum and increased in the jejunum to a maximum 2 d after hatch, then decreased. Delayed access to feed after hatch depressed mucosal development for several days, with the duodenum generally reaching control values earlier than the jejunum. Morphological changes following delayed access to feed included some clumping of microvilli on Day 1 after hatching and abnormal crypt structure between Days 7 and 9. Deutectomy resulted in initial decreased intestinal growth, but this was compensated for by 6 to 8 d in the duodenum, after which development was parallel to that of normal chicks. It appears that nutrient supply from yolk is less crucial for mucosal development then withholding feed for 36 h, which delays normal intestinal development.