A review is given of the occurrence of poxviruses in different bird species. The first publications appeared in Europe around 1850. At that time, pox as a definite disease entity was diagnosed on the basis of clinical signs, while later the detection of Bollinger's inclusion bodies (1877) allowed an aetiological diagnosis by microscopically visible viral aggregates. Virus isolation in embryonated chicken eggs and direct electron microscopy gained importance as diagnostic tools in the 1950s. Also briefly described are avipoxvirus taxonomy, virus characteristics, clinical signs, modes of prevention and diagnostic procedures. Of the approximately 9000 bird species, about 232 species in 23 orders have been reported to have acquired a natural poxvirus infection. However, it is likely that many more birds are susceptible to avipoxviruses.