NOWADAYS, to many young physicians pertussis is a forgotten illness. Very recently, one member of our department who was visiting professor at a Children's Medical Center was presented with an infant suffering from a spasmodic cough. Numerous procedures including bronchoscopy and lung biopsy had been performed to establish a diagnosis. Pertussis, the condition with which the child was afflicted, had not been considered in the differential diagnosis. Many communicable diseases, which formerly contributed to a large proportion of hospitalized patients and caused considerable morbidity and mortality, have lost their importance to the modern physician. Pertussis has followed the course of these events. With the advent of improved care, mass immunization, and antimicrobial therapy, the frequency of pertussis has been altered significantly and its mortality rate has been markedly reduced. However, during the first year of life it represents a very dangerous condition, causing more deaths in this age group than