Cereal grains constitute the greatest proportion of most practical poultry diets. As dietary components, cereal grains provide most of the dietary energy and help to support the development of the structural and functional integrity of the digestive tract. However, many cereal grains contain one or more deleterious factors, which may negatively affect the structural and functional development of the gut. Some of the key factors are carbohydrate in nature, but there are non-carbohydrate fractions which may actually not provide any nutrients but function mainly as anti-nutrients. This chapter broadly explores the normal structure and function of the digestive tract in poultry in the absence of dietary factors. It then highlights the nature of the key components of cereal grains, particularly the components that may influence the development of intestinal structure and function. Finally, the chapter examines the role of cereal grain components on poultry gut function and the possible mechanisms by which these interactions take place.