Mycoplasma are a successful group of pathogens because of their ability to enter and colonise a host, whilst, at the same time, evading the bird's immune response. Mycoplasma iowae (MI) is no exception and, while mostly being a pathogen of turkeys, it can be found in other domestic poultry. It has the added ability of being able to induce a transient immune suppression situation, and this may result in a low to undetectable humoral immune response, giving it the capacity to conceal itself from the immune system. This makes MI both difficult to diagnose and control. The organism has a range of strain dependent pathogenicities and when it is pathogenic, it is primarily found in the embryo and growing poult. This leads to a range of clinical presentations such as decreased hatchability (due to higher than expected embryonic mortality) and stunting and leg abnormalities in the growing poult. As a consequence of the significant variation in pathogenicity of field strain isolates, the isolation of a non-pathogenic MI may conceal the true origin of possible embryo and poult health issues. Control of pathogenic MI at the commercial level is primarily through sourcing pathogenic MI free stock and the maintenance of appropriate biosecurity levels.