Gastrointestinal tumours are an excellent model for the investigation of hereditary factors in cancer. Epidemiological studies on high risk population (China, Iran) evidenced a strong familiarity for esophageal cancer with up to 60% of the affected patients reporting a positive familiary history. About 10-15% of gastric cancer patients show a positive familiary history for this neoplasm. The proportion is even higher for the "diffuse" hystological type. Gastric cancer belongs to the neoplastic spectrum of hereditary nonpolyposis colorectal cancer, a genetic disease with an autosomal dominant pattern of inheritance. Familial polyposis coli and hereditary nonpolyposis colorectal cancer are the two main hereditary colon cancer syndromes. Familiar aggregation have been observed in about 10% of colorectal cancer cases. As for pancreatic cancer, anedoctal reports and one case control study have shown an increased risk of pancreatic carcinoma in patients with a positive family history both for all cancers (relative risk, RR, 2), and specific for pancreatic cancer (RR: 5).