Histilogical, ultrastructural and histochemical studies were conducted on the small intestine of 50 Blanc de Bouscat male rabbits; the age varied between 0-30 days. The result showed that the progress in age has a pronounced effect on the shape and length of the intestinal villi of the small intestine. The mucosa of the small intestine was lined by simple striated columnar epithelium with prominent goblet cells. The crypts opened adjacent to the bases of the villi as simple, branched, tubular invaginations. The mucosa of the small intestine was covered by columnar cells that contained apical microvilli, oval nucleus, dilated cisternae of rough endoplasmic reticulum, Golgi apparatus, vacuoles and electron dense material in all age groups. The crypts showed some epithelial cells with dilated intercellular spaces and contained apical microvilli, mitochondria, granules with electron dense material, rough endoplasmic reticulum and elongated nucleus. There were a few cells with spherical secretory granules of different size above the nucleus and other cells of polymorphic secretory granules of different sizes beneath and lateral to the nucleus. Positive reaction to PAS diastase resistant material and diastase-digested material (glycogen) was clearly seen in the surface and crypts epithelial cells of different ages.