Enzootic pneumonia is a chronical respiratory disease caused by Mycoplasma hyopneumoniae. It results in considerable economical losses for the swine industry in America and Europe. This disease delays growth of the infected pig and reduces its immunity, decreasing the efficiency of vaccination programs, particularly against pathogens of the respiratory tract. Together with strict husbandry, the controlled administration of antibiotics is used against M. hyopneumoniae. But the latter methods is costly and raises the problem of antibiotics resistant pathogens. Vaccination appears an interesting alternative. The searchers wanted to identify membrane proteins of M. hyopneumoniae that could trigger protective immunity. The searchers developed tools for making a subunit protective vaccine. Recombinant fusion proteins of three M. hyopneumoniae membrane proteins (p46, p65 and p97) were produced by genetic engineering with E. coli. These recombinant proteins were used for the development of monoclonal antibodies and diagnostic tests. Also, the recombinant proteins were administered to young piglets to assess their immunity response. The recombinant protein p46 seemed to be a good target antigen for serological diagnostic tests. Furthermore, the recombinant proteins p46 and p97 proved to be very strongly antigenic (more than p65), as shown by the results of a challenge infection with a virulent strain of M. hyopneumoniae. The lungs of pigs vaccinated with the recombinant proteins showed significantly less lesions than those of non-vaccinated pigs, threee weeks after the challenge infection. This research represents an important step towards control of M. hyopneumoniae in swine, particularly with regards to subunit vaccines developed with recombinant proteins.