The objectives of this study were: to estimate the frequency of pigs that were seropositive to porcine influenza virus (PIV), Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae for each phase of production; as well as to determine the frequency of the most common serotypes of A. pleuropneumoniae and subtypes of PIV in fattening pigs. A cross-sectional study was carried out in 25 complete-cycle farms in the state of Yucatan, Mexico.