The immunogenicity and safety of 3 serials of a canine parainfluenza (CPI) virus-Bordetella bronchiseptica vaccine was evaluated. Each serial was used to vaccinate 10 dogs with single doses given intranasally. The 30 vaccinated and 10 nonvaccinated controls dogs were challenge exposed with aerosols of virulent CPI virus and B bronchiseptica at 18 days and at 21 days, respectively, after vaccination. After challenge exposure, none of the 30 vaccinated dogs had clinical signs of disease; however, 9 of the 10 nonvaccinated dogs developed coughing problems. The CPI virus was isolated from nasal swab specimens obtained from nonvaccinated dogs on an average of 5.1 days after challenge exposure, but was not isolated from any of the specimens obtained from the vaccinated dogs. Bordetella bronchiseptica was isolated from nasal swab specimens obtained from both vaccinated and nonvaccinated dogs up to 18 days after challenge exposure. The erythrocyte sedimentation rates and total leukocyte counts for control dogs were generally increased, in contrast to those for the vaccinated groups. Dogs showed a primary serologic response to CPI virus and B bronchiseptica after vaccination and an anamnestic response to the bacterium after challenge exposure. Adverse local or systemic reactions attributable to the bivalent vaccine were not observed in the vaccinated dogs.