Since 2009, Poland has had a TB-free status, although over the last seven years 12-34 cases of bovine TB have been recorded annually. In 2009-2012 the largest number of cattle infected with Mycobacterium bovis and Mycobacterium caprae were culled in Masovian Voivodeship. Likewise, the largest number of sources of this zoonosis were recorded in that voivodeship. The vicinity of farms where bTB was found indicated that it could have been transmitted between their herds. The aim of this study was to characterise the molecular patterns of bovine bacillus strains isolated from cattle in Masovian Voivodeship and the molecular relationships between them. The material for microbiological examination came from 38 cattle (Bos taurus) located in 7 counties of Masovian Voivodeship. These 38 strains of MTBC were further identified as M. bovis (24 isolates; 63%) and M. caprae (14 isolates; 37%). A two-step genotyping analysis of the 38 MTBC strains identified 24 molecular patterns, closely related phylogenetically, which were assigned to 8 clusters of 2-6 strains. Sources of transmission were identified in 8 out of 13 herds examined in the 7 counties of Masovian Voivodeship. The results of the genotyping analysis excluded the possibility of TB transmission between different herds in Masovian Voivodeship. It was proved, however, that TB had been transmitted between animals bred on one of the farms.