Eosinophilic esophagitis (EoE) is a chronic immune/antigen-mediated disorder characterized by eosinophilic infiltration of the esophageal wall leading to inflammation and progressive swelling of the esophagus. In this first of a two-part video, Gary Falk, MD, MS, of Penn Gastroenterology discusses the diagnosis and recognition of EoE, including its distinction from esophageal eosinophilia, a separate and distinct disorder, and its clinical presentation.