<p>&nbsp;</p><p><em>The research goal </em>is to determine clinical, endoscopic and morphological signs of chronic duodenitis in children. <em>Materials and methods: </em>The diagnostic value of molecular markers has been revealed by immunohistochemical research of biopsy. It has been received from endoscopic examination of 32 children aged from 3 to 17 years old with chronic duodenitis. Morphometric investigation of markers expression has been carried out by means of analyzing system of digital images of Mikrovizor medical uVizo-103. <em>Results: </em>The index of proliferation has been higher in cells of cover epithelium than in glands. The inductor expression of apoptosis Bax has been poorly expressed in both groups of patients. It has been proved that proliferative processes are predominant in this pathology. <em>Conclusion: </em>It has been found out that proliferation of significant activity in the cover epithelium accompanies the development of preatrophic processes in children with chronic duodenitis. The greater degree of regeneration has been marked in crypts.</p>