Objective.Magnification endoscopy with acetic acid or dye for diagnosis of Barrett’s esophagus is presently undergoing clinical evaluation.Current studies report good accuracy in predicting specialized intestinal metaplasia.To date,however,there is no definitive information on the inter-and intra-observer variability of these methods applied to the diagnosis of normal and dysplastic Barrett’s mucosa.Material and methods.Sixty patients with endoscopically suspected Barrett’s esophagus were investigated prospectively with the zoom endoscope after contrast enhancement of the mucosa with 1.5%acetic acid.Two hundred and twenty-three enlarged and histologically investigated areas of gastric,cardiac,normal and dysplastic Barrett’s mucosa were photodocumented and in randomized sequence presented to 4 endoscopists in a blinded manner(2 with and 2 without experience of zoom endoscopy for evaluation).The reference for the first evaluation(A1)was standard endoscopic photographs of the respective,histologically confirmed mucosal entity.In a second evaluation(A2),the pictures were again interpreted by the same blinded investigators,but this time a modified pit-pattern classification as proposed by Sharma et al.was employed as the evaluation reference.Results.The diagnostic sensitivity for specialized intestinal metaplasia and dysplasia in Barrett’s esophagus calculated for the A1 evaluation ranged-investigator dependently-from 54.9%to 80.7%and for A2 from 42.2%to 81.5%.The inter-and intra-observer variability for the evaluation procedure A1 and A2 was high(all kappa values < 0.4).In particular,the inexperienced investigators demonstrated high intra-observer variability and low sensitivity in comparison with the experienced investigators.Conclusions.The diagnosis of Barrett’s mucosa using enhanced magnification endoscopy after acetic acid instillation is associated with a high level of interobserver variability.One reason is a frequent mismatch between cardiac mucosa and non-dysplastic Barrett’s mucosa. Objective.Magnification endoscopy with acetic acid or dye for diagnosis of Barrett’s esophagus is presently under clinical evaluation. Current studies report good accuracy in predicting specialized intestinal metaplasia. To date, however, there is no definitive information on the inter-and intra-observer variability of these methods applied to the diagnosis of normal and dysplastic Barrett’s mucosa. Material and methods. Sixty patients with endoscopically suspected Barrett’s esophagus were investigated prospectively with the zoom endoscope after contrast enhancement of the mucosa with 1.5% acetic acid.Two hundred and twenty-three enlarged and histologically investigated areas of gastric, cardiac, normal and dysplastic Barrett’s mucosa were photodocumented and in randomized sequence presented to 4 endoscopists in a blinded manner (2 with and 2 without experience of zoom endoscopy for evaluation). The reference for the first evaluation ( A1) was standard endoscopic photographs of the respective, h istologically confirmed mucosal entity. In a second evaluation (A2), the pictures were again interpreted by the same blinded investigators, but this time a modified pit-pattern classification as proposed by Sharma et al. was employed as the evaluation reference. Results. diagnostic sensitivity for specialized intestinal metaplasia and dysplasia in Barrett’s esophagus calculated for the A1 evaluation ranged-investigator dependently-from 54.9% to 80.7% and for A2 from 42.2% to 81.5%. The inter-and intra-observer variability for the evaluation procedure A1 and A2 was high (all kappa values ​​<0.4) .In particular, the inexperienced investigators demonstrated high intra-observer variability and low sensitivity in comparison with the experienced investigators. Conclusions. The diagnosis of Barrett’s mucosa using enhanced magnification endoscopy after acetic acid instillation is associated with a high level of interobserver variability. One reason is a frequent mismatch between cardiac mucosa and non-dysplastic Barrett’s mucosa.