Gastric cancer is the cancer that usually originates from the cells that line the stomach. The cancer may start as a polyp or an ulcer that initially may not cause any symptom or may cause bleeding or pain. Risk factors for gastric cancer are smoking, bacterial infection and acid reflux. Stomach cancer can also occur in the proximal part of the stomach which is close to esophagus. Esophageal cancer is a cancer that primarily develops in the esophagus. Ways of diagnosing stomach cancer include barium swallow, which examines the esophagus, stomach and duodenum, esophagogastroduodenoscopy, endoscopic ultrasound, computed tomography scan, fecal occult blood test, etc. This book brings forth some of the unexplored aspects of esophageal and gastric cancers. Also included herein is a detailed explanation of the various methods used for the diagnosis and treatment of these cancers. The extensive content of this book provides the readers with a thorough understanding of the subject.