The origin and biologic significance of cardiac gastric mucosa are controversial. Traditionally, it has been considered native mucosa and part of normal foregut development. It has been recently suggested that cardiac mucosa is present only as a metaplastic response to gastroesophageal reflux disease and therefore always abnormal. We evaluated the esophagogastric junction in 100 pediatric autopsy samples to determine the existence, characteristics, and length of pure cardiac mucosa at different ages. No patient had a history of gastroesophageal reflux disease. Cardiac mucosa immediately distal and contiguous to the esophageal squamous mucosa was identified in all 100 samples, varying in length from 0.1 to 3 mm; the mean length was 1 mm. There was an inverse correlation between patient age and length of cardiac mucosa; gender had no influence on measured length. Three patients had mild to moderate histologic esophagitis; two had gastritis. No metaplastic features or Helicobacter pylori were identified. These findings support the concept that there is a normal, variably narrow developmental zone at the esophagogastric junction covered by cardiac mucosa and is present at birth. When cardiac type mucosa is found in biopsy material, it does not necessarily represent evidence of a mucosal metaplastic response to gastroesophageal reflux disease.