The aim of this study was to detect Mycoplasma species in the respiratory tract of 110, 310 and 510 day-old groups of cattle by serological, bacteriological and histopathological investigations. Antibodies against M. bovis were found in 75% of the 110 day-old, in 50%--of the 310 day-old and in 55%--of the 510 day-old groups of cattle. Bacteriological examination of the samples from nasal cavities revealed that Mycoplasma carriers were found in 60% of the 110 day-old group of cattle, 40% of the 310 day-old and 40% of the 510 day-old group of cattle. Using the PCR method Mycoplasma was isolated from 25% of lung samples of the 510 day-old group of cattle. Mycoplasma bovis and Mycoplasma dispar were confirmed by serological investigations. Foci of bronchointerstitial pneumonia were determined by histopathological examination in 27.5% of lung samples. Mycoplasma bovis was isolated in 72.7% of bronchointerstitial pneumonia cases. Data processing with an SPSS 13.0 statistical package led to the conclusion that Mycoplasma bovis was found more frequently in the 110 day-old group of cattle (the youngest age group in this study) rather than in the 310 and 510 day-old groups of cattle (chi2 = 6.531; p = 0.038). The results obtained led to the conclusion that serological, bacteriological and histopathological examinations are important in detecting particular animal--carriers of Mycoplasma.