Four nine- to 11-week-old puppies developed respiratory and neurological signs due to an infection with canine adenovirus type 2 (CAV-2); three of these were euthanased. They had moderate, diffuse pneumonia but there were no histological abnormalities in the central nervous system. Adenovirus-specific nucleic acid was detected by PCR in samples of lung and brain and the amplified product was 99·8 per cent homologous with the CAV-2 reference strain Toronto A26/61. The positive PCR result was confirmed by in situ hybridisation in samples of lung, liver and spleen, but not in brain, and CAV was isolated in cell culture from lung material; PCRs for canine distemper virus and canine herpesvirus-specific nucleic acids were negative, but large amounts of Bordetella bronchiseptica were isolated from lung material.