Cattle from several farms in Hungary were investigated for the presence of mycoplasmal infections after the discovery of pulmonary lesions in some animals at slaughter. The pneumonic lesions, which resembled those of contagious bovine pleuropneumonia (cBPP) macroscopically and histologically were found to be caused by Mycoplasma bovis and not Mycoplasma mycoides subspecies mycoides (Mmmsc) which is the causative agent of CBPP. No other bacterial pathogens were isolated. Negative results in complement fixation tests also showed that there was no serological evidence of CBPP. PCR tests for the detection of the M mycoides cluster and specifically for MmmSc were also negative. However, PCR and bacteriological culture detected cases of M bovis and the pneumonias may therefore be attributed to this mycoplasma.