Because of apparent differences in the incidence and epidemiology of pertussis in the United States and Canada, we measured the antibody response to four Bordetella pertussis antigens and to a whole-bacteria preparation in children immunized with American and Canadian whole-cell pertussis vaccines. All infants received combined pertussis, tetanus, and diphtheria vaccines from one of two American manufacturers or a single Canadian manufacturer. The Canadian children received either oral poliomyelitis vaccine, inactivated poliomyelitis vaccine as a separate injection, or a product that combined inactivated poliomyelitis vaccine with diphtheria, tetanus, and pertussis components. The Canadian trivalent diphtheria, tetanus, and pertussis vaccine given with oral poliovirus vaccine induced lower anti-pertussis toxin antibody titers than did the American vaccines (p < or = to 0.05) but higher antifimbriae and anti-69-kilodalton outer-membrane protein (pertactin) antibody titers (p < or = to 0.02). Canadian children immunized with inactivated poliomyelitis vaccine either as a separate injection or as a combined diphtheria, tetanus, and pertussis vaccine had consistently lower pertussis antibody titers than did those who received oral poliomyelitis vaccine (p < or = 0.001). We conclude that there is a wide range of antibody responses to B. pertussis antigens after immunization with various whole-cell pertussis vaccines, and that these responses may be influenced by concurrent administration of other vaccines.