Gastrointestinal pathology emerged as a subspecialty in the mid-to-late 1980s, coincident with utilization of endoscopy with mucosal biopsy for diagnosis and management of patients with gastrointestinal disorders. The widespread availability of endoscopy coupled with advances in tissue acquisition techniques have drastically increased the number and variety of gastrointestinal samples pathologists encounter in daily practice. As a result, pathologists are now required to provide comprehensive diagnostic information based on review of scant material. Classification of tumors is often completed based on interpretation of immunohistochemical stains coupled with molecular analyses to identify druggable targets or underlying germline conditions. Pathologists also direct the evaluation of patients with gastrointestinal complaints, particularly when patients have persistent symptoms or are immunosuppressed. Thus, they must be able to hone in on key features present in biopsy material in order to narrow the differential diagnosis and better direct patient care. This course is intended to address these needs in a succinct and pragmatic fashion.