Inclusion body hepatitis (IBH) occurred on a pigeon farm of Japan. Basophilic and/or eosinophilic inclusion bodies were found in nuclei of many hepatocytes of all the four pigeons examined pathologically. The same inclusions were seen in epithelial cells of the uriniferous tubules and enterocytes of the small intestine. Ultrastructurally, the hepatic inclusions had viral particles morphologically identical to adenoviruses. The inoculum prepared from the affected liver produced neither cytopathic effects in chick embryo fibroblasts nor pock lesions on chorioallantoic membranes of developing chick embryos.