The purpose of this study is to assess the incidence of adverse drug reactions (ADR) leading to call an emergency medical dispatching centre.A prospective, observational, monocentric clinical study performed over a 2-year period (2011-2012) in a French prehospital emergency dispatching centre, the Service d'Aide Médicale Urgente (SAMU) covering 1,156,000 inhabitants. All adult patients (age≥18) who called for any cause were included. We created an electronic trigger 'iatrogenic event' implemented by the dispatching physician for each suspected case of ADR, then we completed the analyses of all the cases with a chief complain represented in more than 1% of the triggered cases. The primary outcome variable was the occurrence of any possible ADR. We then used the French method of causal relationship assessment.The SAMU dispatched 339,915 calls during the study. In total, 1,467 ADRs were identified, representing 0.95% (CI 95% 0.90-1.00%) of cases. ADRs were as serious (SADR) in 51.06% (CI 95% 48.45-53.67%) of cases. The major ADR observed was haemorrhage, (42.81% (CI 95% 40.62-45.00%), n=628) followed by allergy, hypoglycaemia, vomiting, dizziness and drowsiness. The class of drugs most frequently involved was antithrombotic (43.69% (CI 95% 41.45-45.93%), n=641), followed by insulin (17.98% (CI 95%:17.06-18.90%), n=264).Emergency calls concerning ADRs were estimated as 9/1,000, and one out of two is serious.