Leghorn breeder chickens, which had received live infectious bursal disease (IBDV) virus vaccine at 12 weeks of age and had been injected subcutaneously at 20 weeks of age with an inactivated IBDV oil emulsion vaccine, produced very high antibody titers which persisted for at least 9 months and were more uniform than those obtained from breeders receiving only the live IBDV vaccine. Breeders vaccinated with the inactivated IBDV oil emulsion vaccine at 12 and 20 weeks of age had antibody titers higher than breeders which received only the live IBDV vaccine at 12 weeks of age; titers were lower than in the group which received both the live and inactivated oil emulsion IBDV vaccines. Maternal antibody levels in chickens derived from parent flocks vaccinated with the inactivated oil emulsion IBDV vaccine were higher and more uniform than in chickens derived from parent flocks vaccinated with the live IBDV vaccine. Maternal antibody persisted longer in chickens derived from parent flocks vaccinated at 20 weeks of age with the inactivated oil emulsion IBDV vaccine than in chickens vaccinated by the other procedures. The titers remained quite high up to 16 days of age.