The data concerning the degree of adhesion and antagonism of microorganisms of oral cavity in patients with malignant neoplasms of tongue is presented. it is established that pathogenic and conditionally pathogenic microflora has more mainly high and less infrequent degree of adhesion. the normal microflora has average and low degree of adhesion. About 90% of lactobacilla of oral cavity manifest no antagonism concerning pathogenic and conditionally pathogenic microorganisms. The antagonism of enterobacteria, staphylococcii and lactobacilla is absent. The staphylococci, including producing β-lactamase and methicillin-resistant ones, in 95% of cases are antagonists to streptococcii. The clinical isolates Candida albicans show antagonistic activity related to 90% of lactobacilli and 20°% of streptococci.