Gastric cancer is a common disease worldwide, typically associated with acquired chronic inflammation in the stomach, related in most instances to infection by Helicobacter pylori. A small percentage of cases occurs in familial clusters, and some of these can be linked to specific germline mutations. This article reviews the historical background to the current understanding of familial gastric cancer, focuses on the entity of hereditary diffuse gastric cancer, and also reviews the risks for gastric cancer related to a number of other familial genetic diseases. Keywords: Gastric cancer, E-cadherin, H pylori, Diffuse Gastric Cancer, GAPPS, Lynch Syndrome, Li-Fraumeni Syndrome, Peutz-Jeghers Syndrome, Juvenile Polyposis Syndrome