For more than 15 years, over 95% of 2-year-olds have received the three doses required for the primary pertussis vaccination series. The disease has become rare in children but persists among infants too young to receive the vaccine and among adolescents and adults whose immunity acquired through illness or vaccination has waned. The disease is severe in infants, which led, in April 1996, to the resumption of surveillance after a 10-year hiatus, through a metropolitan pediatric hospital network. Its objective is to monitor the evolution of severe forms of pertussis in children and to assess the impact of changes in vaccination strategy on the epidemiology of the disease. This article presents the results of the surveillance conducted by this network in 2004. (Introduction)