Gastric cancer is one of the most common neoplasias in the world and remains an important cause of cancer-related mortality. Vast resources have been invested in the study of the molecular events driving the development and progression of gastric tumors. Gastric cancer is known to result from an interaction between host and environmental factors. The present review will discuss the most how genetic and epigenetic changes contribute to gastric carcinogenesis and their potential for developing novel diagnostic and therapeutic tools.