A comparison of the results of repeated immunological surveys with the notification of morbidity and mortality to pertussis and parapertussis revealed direct dependence and simultaneously confirmed the effectiveness of Czechoslovak vaccine. Immunological surveys should be continued in spite of the fact that morbidity of pertussis is low at present, because immunological surveys may lead to timely detection of shortcomings in the quality of vaccination and vaccine. The results after 14 years of systematic vaccination and revaccination and consequent follow-up to the state of immunity in the population and of other factors in the pertussis surveillance programme rank among the other achievements of epidemiology and hygiene in Czechoslovak health services. Contemporary immunological surveys show that the state of immunity in Czechoslovak child population is such as to exclude the occurrence of pertussis in epidemics in the nearest future. The situation is different in parapertussis where epidemic incidence is still possible and where epidemics regularly occur in children of prae-school age.