Esophagitis in infancy and childhood produces characteristic histologic changes in the mucosa and lamina propria of the distal esophagus. The use of biopsy in addition to endoscopic evaluation considerably enhances the accuracy of the diagnosis of esophagitis, particularly when the degree of inflammatory change is mild. In the absence of severe inflammatory changes, such as ulceration or mucosal slough, esophageal biopsy appears to be essential for the accurate diagnosis of esophagitis. In children of any age with GER who have symptoms of esophagitis, antacid therapy and vigorous efforts to control reflux are indicated. Failure to respond to this program is an indication for esophageal biopsy to confirm or rule out the presence of esophagitis. The degree of inflammatory change in the biopsy is a reliable guide to expected response to antiacid therapy.