The RFLP-IS6110 assay was used to genotype 67 Mycobacterium tuberculosis isolated from different specimens (including intraoperative ones) of 24 patients operated on for chronic progressive pulmonary tuberculosis who lived in north-western Russia. More than half (53%) of 17 types of RFLP profiles of isolates are identical and typical of M. tuberculosis of the Beijing family. Comparing the results of isolate genotyping with clinical, microbiological, and pathomorphological findings allows cases of endogenous reactivation to be differentiated from exogenous (nosocomial, in particular) reinfection in recurrence. Beijing genotype strains are shown to cause more severe unarrested course of drug-resistant fibrocavernous tuberculosis. At the same time such strains are more frequently detected in relatively young persons with a shorter duration of the disease, which reflects current clonal Beijing genotype dissemination that present a severe epidemiological hazard.