Evaluation of acellular pertussis vaccine and components of B. pertussis was performed by the use of an in vivo assay system consisting of the mouse aerosol challenge test and the antibody responses in mice. Acellular pertussis vaccine (ACP), pertussis toxin (PT), filamentous hemagglutinin (FHA), fimbriae or whole cell vaccine (WPV) were challenged intrapulmonarily with B. pertussis. The number of colonies of B. pertussis in the lungs of the mice were counted. 1. Does response relationships were observed between the dose of the vaccines, APV or WPV, and B. pertussis colony counts in the lungs of mice injected with one of the vaccines or immunogens. Higher doses of the vaccines or immunogens resulted in reduced numbers of colonies of B. pertussis in the lungs of mice. 2. When the amounts of total protein nitrogen were in the same range, APV and a mixture of PT and FHA showed higher protective efficacy than PT or FHA alone. 3. Rises in antibody titers were observed in mice injected with APV, WPV, PT or FHA.