The methods used for recovering mycoplasmas from birds are broadly similar to those described for other animals and for humans. Mycoplasmas are important causes of disease and loss of production in intensively reared poultry, particularly in those that are under environmental stress (1 ). Mycoplasma gallisepticum affects chickens and turkeys and is the most important of the pathogenic avian mycoplasmas. It is especially serious in broiler (meat-type) chickens in which it often acts synergistically with other agents, such as respiratory viruses or pathogenic strains of Escherichia coli to provoke chronic respiratory disease. In laying birds, it may also cause loss of egg production. Mycoplasma synoviae affects chickens and turkeys and, under some circumstances, can contribute toward respiratory disease, whereas in heavy birds, it may cause synovitis and arthritis. Mycoplasma meleagridis is specific for its host, the turkey, in which it can cause reduced hatchability and reduced viability of young birds and can also cause disease of the air sacs. A fourth avian mycoplasma pathogen is Mycoplasma iowae , but its economic effects appear to be largely confined to the turkey embryo, in which some strains are lethal. The chicken and turkey industries have invested heavily in the production of primary breeding stock that are free from these pathogens, and they also maintain expensive biosecurity and serological surveillance programs to guard against reinfection that will prejudice their home and export trade.