A comparison was made between four inactivated infectious bursal disease (IBD) oil emulsion vaccines. Vaccine A, which was prepared from antigen derived from bursae of Fabricius, stimulated higher levels of IBD gel diffusion titres than vaccines B, C and D, which were prepared from antigens derived from embryo fluids. The progeny of parents vaccinated with vaccine A resisted IBD challenge for eight days longer than the progeny of any of the other vaccinated parents.