Ornithobacterium rhinotracheale -bacterium (ORT) is associated with respiratory infections in chickens and turkeys. It is quite a fairly recently discovered bacterium, the first report is from 1981. The bacterium was named in 1994. ORT has a worldwide prevalence. In Finland ORT has been suspected in several cases of respi-ratory infection in poultry but the bacterium has never been isolated in Finland, ORT is both a primary and secondary pathogen in poultry. It causes mortality, mild or severe respiratory infections, decreased growth rate, drop in egg production, and increases condemnation rate. Usually the disease is multifactorial and other pathogens and nonoptimal environmental factors greatly affect the outcome. The presumptive diagnosis is based on typical clinical signs and pathological lesions. For definitive diagnosis, evidence of ORT-bacterium is needed either by culture or by other methods. Isolation of ORT is difficult, because the bacteria need to be iso-lated early in the course of the disease and they grow slowly on agar. Serology can be better used for problem screening studies, but its use is limited in diagnosing a single case. In Finland, serum samples from a few tur-key flocks have been examined for the presence of ORT-antibodies with positive results. Treatment of ORT infec-tions is difficult due to the multifactorial nature of the disease and the relative ease the ORT-bacteria develop antibiotic resistance. Antibiotic treatment should always be based on a sensitivity test. Vaccines against ORT have been developed during recent years. Currently, there are vaccines that can be used for the vaccination of breeder flocks to give passive immunity to their progeny. Since treatment of ORT is difficult and vaccines are still under development, an efficient prevention of the disease is crucial. Cleaning and disinfecting houses thor-oughly between flocks, all-in-all-out system, optimal environmental conditions, especially good ventilation and prevention of other infections are very important in the prevention of ORT infection.