A standard of care for the recognition and management of patients and families with hereditary gastrointestinal cancer syndromes is emerging, and both gastroenterologists and genetic counselors have an important role. This Review considers these roles and outlines the partnership needed between gastroenterologists and genetic counselors. The role of the gastroenterologist involves careful sampling of polyps and tumors, and requires a basic working knowledge of the features of hereditary gastrointestinal cancer syndromes. The role of the genetic counselor is to gather and synthesize family history and pathology information, formulate a genetic differential diagnosis, determine a genetic testing strategy, guide medical management and help patients communicate information to their relatives. Managing the complex logistics of testing the best candidate in the family, facilitating informed consent, outlining costs to patients and interpreting test results are also responsibilities assumed by genetic counselors. In addition, genetic counselors help physicians meet their ethical and medicolegal obligations with respect to patient management and family communication. Referral schemata for patients with polyposis and nonpolyposis features are presented in this Review, along with comprehensive tables that outline the features of well-known and rare syndromes that heighten the risk of gastrointestinal malignancy.