Patients with eosinophilic esophagitis present with symptoms similar to those from gastroesophageal reflux disease along with dense esophageal eosinophilia (normal gastric and duodenal biopsies) that persist despite aggressive acid blockade. The dramatic increase in prevalence of eosinophilic esophagitis over the past several years provides clinicians with a new explanation for previously unexplained dysphagia, food impaction, vomiting, and abdominal pain. As a product of this recognition, an increasing number of basic and translational studies are building a new understanding of the pathogenesis of esophageal eosinophilia. This review addresses recent studies that define clinical features, genetic predisposition, pathogenetic mechanisms, and treatment options for eosinophilic esophagitis.