Use of killed whole-cell Bordetella pertussis vaccines has been a major factor in control of symptomatic whooping cough (pertussis). In the UK, diminished public confidence in the safety of this vaccine led to a reduction in vaccine acceptance which correlated with an increase in the incidence of pertussis. There is a need for acellular pertussis vaccines of low toxicity which, ideally, will prevent colonization and also protect against the disease symptoms. Vaccine design can rely increasingly on knowledge of the roles of individual bacterial components in the pathogenesis of pertussis. Serotype-specific agglutinogens 2 and 3 (fimbriae) and filamentous haemagglutinin are among surface components of B. pertussis which probably mediate adhesion to the respiratory mucosa. Systemic effects of pertussis can largely be attributed to the lymphocytosis promoting factor (pertussis toxin). Vaccines containing detoxified toxin plus one or more purified adhesins are envisaged at present.