Hereditary Diffuse Gastric Cancer (HDGC) is an autosomal dominant cancer syndrome that is characterised by a high prevalence of diffuse gastric cancer and lobular breast cancer. It is largely caused by inactivating germline mutations in the tumour suppressor gene CDH1, although pathogenic variants in CTNNA1 occur in a minority of HDGC families. Here, the International Gastric Cancer Linkage Consortium (IGCLC) has updated practice guidelines for HDGC, recognising the emerging evidence of variability in gastric cancer risk between HDGC families, the growing capability of endoscopic and histological surveillance in HDGC and greater experience managing long-term sequelae post total gastrectomy in young patients. To redress the balance between the accessibility, cost and acceptance of genetic testing and greater identification of pathogenic variant carriers, the HDGC genetic testing criteria have been relaxed, mainly through less restrictive age limits. Prophylactic total gastrectomy remains the recommended option for gastric cancer risk management in pathogenic CDH1 variant carriers. However, there is increasing confidence from the IGCLC that endoscopic surveillance in expert centres can be safely offered to patients who wish to postpone surgery or to those whose risk is not well defined.