The purpose of the study was to determine the condition of the periodontal tissues in 80 children with various morphological forms of gastritis and duodenitis. The examination included determination of oral hygiene and periodontal status by the simplified Green-Vermillion index, Silness-Low index, papillary-marginal-alveolar index, gingival Muhlemann-Cowell bleeding index, Schiller-Pisarev iodine index. In children with chronic gastritis and duodenitis high incidence of chronic catarrhal gingivitis (85.0%) was revealed. At the same time it was pointed out that inflammation in the periodontal tissues correlated with changes in the gastroduodenal mucosa. In 65.4% of children with superficial gastritis and duodenitis, chronic catarrhal gingivitis (localized in 38.5% of cases, generalized in 26.9%) was observed. In 94.4% of all children with diffuse and erosive gastritis and duodenitis, chronic generalized catarrhal gingivitis was observed, and low oral hygiene level was revealed. The severity and duration of the underlying disease aggravated clinical manifestations of chronic catarrhal gingivitis in children with lesions of the upper gastrointestinal tract.