In Poland vaccination against diphtheria, tetanus and pertussis (DTP) is recommended from 2-3 months of age. Three doses at approximately 6-week intervals are given. A booster dose of DTP is given at 19-24 months and boosters of DT at 6 and 14 years. In this study serum samples were obtained from 166 Polish children aged 2 weeks to 14 years. Vaccination status was verified from the children's Health Books. Antibodies were determined against pertussis toxin, filamentous hemagglutinin (FHA), pertactin, tetanus toxoid and diphtheria toxin. Antibodies of maternal original against all five antigens were detected in almost all sera from infants not yet vaccinated. Antibody levels increased with the number of vaccinations given. Children who had recently received the fourth vaccination had the highest antibody levels. Antibody levels decreased with time after the fourth vaccination for all antibodies except FHA. It was concluded that the Polish whole cell pertussis vaccine stimulates antibodies against pertussis toxin, FHA and pertactin, but that antibodies against FHA probably also are stimulated by cross-reacting antigens. Diphtheria toxin and tetanus toxoid antibodies were above protective levels in all vaccinated children, but the long-term decreases justify the booster dose at 14 years. Twenty-five of 166 children (15%) had a vaccination status which deviated from recommendations demonstrating a need to increase the vaccination rate.