Abstract
No bacteria were observed in an epizootic of lethal pneumonia in guineapigs. Necrotic bronchitis and bronchiolitis with basophilic intranuclear inclusion bodies in bronchial epithelial cells were characteristic. Although adenovirus infection of guineapigs has not previously been reported, histological findings paralleled those found in adenovirus infections of other animals including man. Virus particles found by electron-microscopical examination of the lung tissue closely resembled adenoviruses. The disease seemed to have a low contagiousness, a low morbidity (about 0·7%), but an acute course and a high mortality (100%).