The aim of the study was to determine the prevalence of Mycoplasma bovis infection in clinical cases of bovine respiratory disease (BRD) in 2011. There were examined 841 serum samples and 41 nasal swabs and lungs of cattle from different farms of six regions of Poland (13 provinces). The obtained results indicated that the mean prevalence of M. bovis infection in Polish cattle population suffering from BRD was 64.3% and among them 8.4% of the animals were highly positive. On the other hand, in particular regions, it altered - 72.0% in east region, 52.7% in central region, 66.4% in south region, 64.1% in north-west region, 56.5% in north region, and 58.8% in south-west region. It should be added that within the presented regions, the highest values (82.4%) were reported in south region (Malopolskie province), whereas the lowest ones (42.9%) were in east region (Lubelskie province). However, field strains of M. bovis were isolated from the lungs of affected cattle only in the north-west region of Poland (Zachodniopomorskie province).