The purpose of this study was to investigate the protective effects of the modified live vaccines against canine Bordetella bronchiseptica(Bb) and canine parainfluenza virus(CPIV) in puppies by nasal administration. A total of 24 puppies were classified as 3 groups consisting of 8, and each one was divided into two subgroups; vaccinated (n=4) and unvaccinated(n=4). Group I, group II and group III were challenged with Bb, CPIV, and Bb+CPIV, respectively. In group I vaccinated puppies(n=4) were experi-mentally challenged with Bb 2 weeks after vaccination and unvaccinated puppies(n=4) were experimentally challenged with Bb alone. The same methods of the above were applied for group II and group III. We carried out several studies including serum tests, isolation, and histopathological examination. The vaccinated puppies showed higher antibody titers than unvaccinated puppies and the titer sustained during the experi-mental period. In the isolation test, recovery period was shorter in the vaccinated subgroup than in the other. In clinical signs, the unvaccinated puppies showed the typical signs of tracheobronchitis (coughing, nasal and occular discharge), but another subgroup showed delayed incidence and mild clinical signs. The typical gross lesions and histopathological findings were observed in the unvaccinated puppies. In immuno-histochemical findings, the vaccinated puppies showed little intensive in reaction for CPIV antigen than the other. It could be concluded that intranasal vaccination of modified live Bb and CPIV vaccine to puppies is effective to prevent canine infectious tracheo-bronchitis.