Scientific data concerning clinical peculiarities of chronic catarrhal gingivitis in children with underlying diffuse simple goiter are supplied. It has become a foundation for further investigation of immunological aspects of pathology development on the basis of a comprehensive examination of the oral fluid of children. The scientific data concerning glycoprotein state in the oral cavity and their role in the formation of pathological process in the periodontal tissue with underlying diffuse simple goiter are obtained for the first time. A number of correlation dependences between the local changes of the morphological-functional state of the periodontal tissue and disorders of the protective mechanisms of a specific and nonspecific character were found, by PMA index and levels of sIgA (r=0,72, р<0,05), IgA (r=-0,30, р<0,05), lysozyme activity (r=0,35, р<0,05) in particular, etc. The correlation analysis determined certain mechanisms of formation of chronic catarrhal gingivitis under effect of diffuse simple goiter, and interrelations between the parameters of the local immunity and different glycoprotein fractions of the oral fluid in children in particular – sIgA and hexosamines (r=0,55, р<0,05); lysozyme and fructose (r=-0,51, р<0,05); lysozyme and sialic acids (r=-0,47, р<0,05); IL-1β and hexosamines (r=-0,38, р<0,05). They are indicative of a leading role of immunologic disorders in the development and progression of dental pathology and which become a basis for realization of the common periodontal-pathogenic factors. On the basis of comprehensive clinical-laboratory examinations of children suffering from chronic catarrhal gingivitis and diffuse simple goiter the therapeutic-preventive method concerning this comorbid pathology was substantiated and developed. In addition to the common measures it includes correction of macro-element and trace element metabolism and strengthening of the immune protection of the child’s organism on the systemic and local levels. Original pharmacological correction of chronic catarrhal gingivitis in children with underlying diffuse simple goiter is suggested for the first time. In addition to the common therapeutic-preventive measures it assumes local administration of lysozyme containing antiseptic agent and oral immune modulator against the ground of correction of trace element metabolism by means of a vitamin-mineral medication. New pathogenic ways of chronic catarrhal gingivitis in children with underlying diffuse simple goiter under conditions of maladjustment of local immunological processes are found and the existing ones are supplied with new data. Detection of a number of immunological and biochemical parameters of the oral fluid in children suffering from diffuse simple goiter is suggested which enables to make preclinical diagnostics of inflammatory processes in the gums, specify the degree of functional tension of the local protective mechanisms and probability of development and advance of gingivitis. Key children, chronic catarrhal gingivitis, diffuse simple goiter, oral fluid, immunoglobulins, cytokines, glycoproteins, therapeutic-preventive complex. Branch – medicine.