Gastric adenocarcinoma is among the most common malignancies worldwide. Its etiopathogenesis is complex and, as yet, incompletely understood; however, diet, infection with Helicobacter pylori, and genetic factors are involved. It may be classified into two main types, intestinal and diffuse. The intestinal type has decreased in incidence, whereas the diffuse tumors as well as those confined to the cardia are increasing. Numerous conditions, such as gastritis, gastric atrophy, and intestinal metaplasia (IM), are associated with intestinal type gastric cancer in retrospective studies, but only epithelial dysplasia has a positive predictive value for malignancy. These precursor conditions and lesions are analyzed for their clinicopathological significance in this review, which concludes with a brief summary of curable (early) forms of gastric cancer.