Tuberculosis is infectious and socially dependent disease, being now one of the most pressing issues in practical health care. As well the usual types of tuberculosis infection, chemoresistant tuberculosis is spreading rapidly in the world. The WHO estimates that about 500,000 people on the planet are infected with M. tuberculosis, which is resistant to standard anti−tuberculosis drugs. The probability of successful treatment decreases with emergence of new genotypes of M. tuberculosis with total resistance. In the modern epidemiology of tuberculosis, it is important to identify genotypes on certain signs, allowing to address issues such as their origin, identification of the infection source, possible routes and factors of transmission, as well as to reveal cases and spread of resistance to anti−tuberculosis drugs. To evaluate the therapy efficiency of multidrug−resistant tuberculosis patients with revealed genotypic variability during treatment, 10 patients with chemoresistant pulmonary tuberculosis having M. tuberculosis genotypic variability were treated. In these patients, the clinical, laboratory and radiological dynamics of disease in intensive phase of treatment were studied. Analysis of treatment results for patients with chemoresistant tuberculosis with genotypic variability of M. tuberculosis was evaluated by the intoxication syndrome dynamics of, the timing of closure of the decay cavities and cessation of bacterial excretion. The study found that the genotypic variability of M. tuberculosis is characterized by the change of less virulent genotypes of M. tuberculosis to more virulent. Signs of intoxication have been shown to change from less virulent M. tuberculosis genotypes to M. tuberculosis Beijing genotypes. Genotypic variability of mycobacteria in hospital suggests that hospitalization in tuberculosis facilities is a risk of exogenous tuberculosis superinfection. Studying the influence of genotypic variability of M. tuberculosis on the course of multidrug−resistant tuberculosis requires more extensive research, being a very relevant and promising area in phthisiology. Key words: Mycobacterium tuberculosis, genotypic variability, VNTR−genotyping, treatment.