Mycoplasma hyopneumoniae (Mhyo) is an important component of the so called Porcine Respiratory Disease Complex (PRDC). Mhyo infection in pigs is usually monitored through serology. In this study, we compared three ELISAs developed to detect antibodies to Mhyo in swine serum. The main objectives of this study were to differentiate serum antibody profiles of four groups of animals: non-challenged/vaccinated, challenged/vaccinated, challenged/non-vaccinated and non-challenged/non-vaccinated animals.