Gastrointestinal (GI) tract is a hollow tube that extends from oral cavity to anus and is divided into upper GI tract and lower GI tract. The major parts of upper GI tract include oral cavity, esophagus, stomach and duodenum. The major components of lower GI tracts are—small intestine, large intestine, appendix, rectum, and anus. The organs associated with gastrointestinal tract are salivary glands, liver, gallbladder, and pancreas. The wall of the GI tract has four layers and from inside to outside; these layers are mucosa, submucosa, muscle layer, and serosa. The main functions of GI tract are ingestion, mastication of food, deglutition, digestion, absorption, and excretion of undigested food material as feces. Esophageal cancer, stomach, intestine, tumors of intestine, polyps of colon, colorectal cancer—adenocarcinoma, malabsorption syndrome, inflammatory bowel disease, and peritoneum are different types of GI tract disorders, which are discussed in this chapter. At the end of this chapter, self-assessment exercise is also provided in this chapter.