BACKGROUND The pediatric population displays its own pharmacological characteristics, making children vulnerable to adverse drug reactions (ADRs). OBJECTIVE To determine the incidence of ADRs among the pediatric emergency department (PED) population. METHODS This is a descriptive, noncontrolled, prospective, and single-center study, during 4 consecutive months in the PED of Nantes University Hospital. RESULTS Setting up active gathering of data on ADRs enabled 121 reports of 11 095 consultations at the emergency department, which corresponds to an ADR incidence of 1.09%. Digestive and cutaneous reactions made up the majority of reactions judged as being nonserious (53%) and were mainly found in children between 2 -11 years old. Of the serious ADRs, 25% were found in the 12-15-year-old age range because of the drug overdose. The main medications administered, which were responsible for the majority of the ADRs, were an equimolar mix of oxygen and nitrogen monoxide, amoxicillin, and acetaminophen. Three means of collecting data were possible: collecting files data, oral communication, or filling a form, the last being the most used method. CONCLUSIONS This active data gathering shows the incidence and nature of the adverse effects as well as the age distribution in the PED population. It highlights the considerable misuse of medications among young teenagers and the high incidence of overmedication in the younger age group. This work also revealed the need for a better reporting system. Future joint studies should be carried out between clinical and pharmacological departments to optimize communication and the correct use of medications in children.