Background. Violations of indigenous microflora composition associates with a wide variety of gynecological complications. Thus, the qualitative and quantitative composition of lactobacilli and their associative capacity and functional activity may serve as a criterion of microecological well-being in the body. Aim. To study species diversity of lactobacilli in vaginal biotope teenage girls with gynecological pathologies and to assess the extent of their relationship with the combination of diversity profiles associated opportunistic pathogens. Materials and methods. The study included 107 adolescents with reproductive system disorders. The study was conducted with the use of gynecological and general microbiological methods. Results. It was revealed that in vaginal biocenosis of the studied group of teenage girls dominating lactobacilli were Lactobacillus plantarum and L. crispatus, the incidence of other species did not exceed 21 %. Among the representatives of opportunistic pathogenic microflora dominated coccal microflora and Corynebacterium spp., being the part of normal flora of vaginal mucosa. Analysis of species composition revealed a statistically significant relationship between certain types of lactobacilli and opportunistic microorganisms, i.e. lactobacilli showed no antagonistic activity towards the opportunistic microorganisms, and formed symbiotic relationships with them. Conclusions. Most commonness was found among the minor species of lactobacilli (L. iners, L. gasseri, L. jensenii), coagulase-negative staphylococci and fungi of Candida genus, and that increases the risk of transformation of normal microflora in the pathological one.