The esophagus traditionally has been considered a simple conduit for more than 50 tons of foodstuffs ingested during a lifetime. A growing body of literature, however, is defining the dynamic role of esophageal protective mechanisms and is identifying the immunologic milieu present within the squamous mucosa. When the innate protective mechanisms are overcome by an injurious agent, an inflammatory process ensues, and the clinicopathologic features of esophagitis are manifest. This article focuses on features of several causes of esophagitis in children, including peptic disease, duodenogastroesophageal reflux, Crohn's disease, and infection. In addition, a relatively new, but increasingly recognized, entity-eosinophilic esophagitis-is highlighted.