Eosinophilic esophagitis (EE), initially described in children, is now recognized in adults. The prevalence of EE in adults is largely unknown. Our goals were to determine the prevalence of EE in an adult population undergoing esophagogastroduodenoscopy with biopsy as originally reported and on retrospective review, the rate at which EE was present before this diagnosis was readily appreciated, and whether the prevalence of EE has changed over time. We reviewed esophageal biopsy specimens from 1992 to 2004. If there were more than 15 eosinophils per high-power field and confirmatory clinical information was available, EE was diagnosed. The initial (prereview) prevalence was 1.3%; prevalence on retrospective review was 1.7%. Prevalence was higher in later years (3.8%) compared with early years (0.3%). The demographics of our patients with EE are generally similar to what has been reported. Our results suggest the prevalence of EE is increasing and that pathologists provide accurate diagnoses in the face of changing criteria and significance.