Progeny of broiler breeder parent flocks routinely vaccinated with a bivalent inactivated vaccine containing fowl adenovirus serotypes 8 and 11 were challenged with a new strain of fowl adenovirus serotype 9. The new strain is known to cause inclusion body hepatitis in chickens. Results indicated that the current vaccine provided protection from infection to the progeny of the vaccinated parent flocks when challenged with the non-vaccine serotype 9 fowl adenovirus. Twelve fowl adenoviruses were characterized by molecular techniques and virus neutralization assays. The viruses were found to belong to four different fowl adenovirus serotypes: European serotypes 6, 7, 8, and 10.