Gastrointestinal diseases of chicken often have a multiple etiology. The combination of pathogens differs from place to place. Pathology of these diseases rely not only on the host immune status and strain of pathogen, but also on the predisposing factors like season, age of birds, environment temperature, method of rearing, and nutritional plane.Systematic pathological study of the gastrointestinal tract in poultry diseases has not yet been carried out extensively. Realising the paucity of information on the occurrence of such diseases in poultry, a detailed research on "Pathology of gastrointestinal diseases in laying chicken was carried out. Hence, this book will helpful for poultry Scientist to undertake research on gastrointestinal diseases of chicken.