The usage of Mycoplasma gallisepticum oil-emulsion bacterin had a noticeable effect in protection of chicks against air sacculitis. This study was carried out on chicks originating from vaccinated parents. Serum plate agglutination and haema gglutination inhibition titres, the gain in body weight and feed consumption rate were superior in vaccinated broilers from vaccinated dams. It could be concluded that the vaccination of the parents necessate vaccination of the broilers to attain optimal protection against Mycoplasma gallisepticum infection.