On the basis of clinical and endoscopic examination of 31 patients with ankylosing spondylitis (AS) with clinical signs of esophageal lesions, we have found that in these patients erosive lesions of the esophagus occur much more often than in simple gastroesophageal reflux disease (GERD). Esophageal lesions in patients with AS are more severe than in simple GERD — severe erosive esophagitis (of C and D grade) is detected in 43.8 % of patients with erosive and ulcerative lesions of the esophagus against AS. Microscopic examination of biopsy material taken from esophageal mucosa suggests multifactorial mechanism of esophageal lesions in AS, including systemic and local immune inflammation, abnormal microvasculature, excessive proliferation of connective tissue, disseminated sclerotic processes in the wall of the esophagus, reduced number of esophageal glands.