BACKGROUND AND STUDY AIMS: A newly designed magnifying endoscope featuring an endocytoscopy function provided by ultrahigh magnification was evaluated in a pilot study in patients with various types of benign and malignant pathology in the esophagus. PATIENTS AND METHODS: Seventy-five consecutive patients were included in the study from 15 March to 21 December 2005. Twenty-nine patients with specific esophageal lesions that had been detected by regular or narrow-band imaging, or both, were further evaluated using endocytoscopy, followed by tissue biopsy or resection. During the endocytoscopic examinations, the esophageal mucosa was stained with 0.5 % methylene blue. The endocytoscopic findings were graded from 1 to 5 in an endocytoscopic atypia (ECA) classification. The final histopathological diagnoses based on biopsies or resected specimens were as follows: category 1 in the Vienna classification, n = 4; category 2, n = 6; category 3, n = 1; category 4, n = 10; and category 5, n = 7. The endocytoscopic diagnoses were compared with the histopathological diagnoses. RESULTS: Clear endocytoscopic images were obtained in all cases. In definitely malignant lesions, the cell nuclei had an enlarged and irregularly arranged appearance (grade ECA 5). The positive predictive value for malignancy (grades ECA 4 and 5) was 94 %; the false-negative rate was 16.7 %, and the false-positive rate was 6.3 %. The overall accuracy of endocytoscopy for differentiating between nonmalignant tissue (categories 1 - 3 in the Vienna classification) and malignant tissue (categories 4 and 5) was 82 %. CONCLUSIONS: These preliminary results suggest that incorporating endocytoscopy facilities into a standard endoscope may be helpful in characterizing tissue in a variety of esophageal lesions. The potential clinical impact of this method in relation to other gastrointestinal organs requires further study.