Post-resection wound healing, oral microbiota composition and saliva lysozyme activity were assessed in 36 patients with tongue carcinoma before and after surgery with the local application of 2% solution of acid-diluted chitosan in the postoperative period. The microbiocenosis of the oral cavity before treatment in cancer patients was represented by conditionally pathogenic and pathogenic bacteria, whose number is more than 4 lg CFU/cm2, indicating dysbiosis; the lysozyme level was reduced, accounting for 25.4±8.5 µg/ml. After the radical hemi-glossectomy the reduction in the frequency and quantity of conditionally pathogenic and pathogenic microorganisms was statistically determined, as well as an increase in the level of lysozyme of saliva on the 10 day of treatment. Patients receiving local treatment with chitosan showed an increasing number of normal microbiota in 1,5—2 times, and the level of lysozyme in 8 times (amounted to 202.87±56.85 µg/ml).