The pertussis vaccination programme was started in Finland in 1952. Since then the incidence of the disease has decreased. No major epidemics have occurred during the last two decades. The majority of the patients with pertussis are children of school age. Their disease is characterized by prolonged cough without whooping and it is difficult to diagnose. The patients with atypical pertussis are, however, the major reservoir for transmission of the disease to young infants, in whom it can be serious. Recently developed ELISA for measuring antipertussis IgM and IgA antibodies is a valuable aid in the diagnosis of these cases. Pertussis vaccination has been a subject of considerable controversy in recent years. The vaccine used in Finland has proved to be safe and effective. This observation emphasizes the need for careful comparison of the vaccines used in different countries.