The most important mycoplasmas isolated from domestic avian species include Mycoplasma gallisepticum (MG), M. synoviae (MS), M. meleagridis (MM) and M. iowae (MI). MG causes chronic respiratory disease of chickens and infectious sinusitis in turkeys, resulting in economic losses. MS causes infectious synovitis or mild upper respiratory disease. MM infects only turkeys, causing airsacculitis and sub-optimal production and hatchability. MI is associated with reduced hatchability in turkey flocks. Transmission is either direct, from bird to bird or through the egg, or indirect. Diagnosis is based on isolation and identification of mycoplasmas, according to biochemical, serological or molecular biology tests, or serological examination of host sera by slide agglutination, haemagglutination inhibition or enzyme-linked immunosorbent assay (ELISA) tests. Antibiotics (i.e. tetracyclines, macrolides, quinolones and tiamulin) may be used for therapeutic treatment or prophylactic medication. The eradication of mycoplasma infection can be achieved through improvements in hygiene and management practices, therapeutic treatment of breeder layers and/or of hatching eggs and better monitoring procedures.