In spite of their importance as avian pathogens causing important losses in poultry farming, the biochemistry of avian reoviruses has been little investigated. In order to facilitate the handling of these agents in the laboratory, a study was carried out to establish the best conditions both for growing the avian reovirus S1133 in primary cultures of chicken embryo fibroblasts and for purification and storage of viral suspensions. The results indicate that the conditions used currently for the manipulation of mammalian reoviruses are not always the best for handling their avian counterparts. In particular, avian reoviruses are much less stable than mammalian reoviruses, and specific conditions for the purification and storage of avian reoviruses therefore should be used. Furthermore, the instability of avian reovirions may have important implications for the life cycle and pathogenesis of the virus within the animal host.