Carbon monoxide (CO) poisoning is the leading cause of toxic-related deaths in France. This painless, odorless gas acts insidiously, making it all the more difficult to combat. CO poisoning is not subject to mandatory reporting. In a region heavily affected by carbon monoxide poisoning, public health officials in Picardy have, for nearly 10 years, implemented a surveillance and intervention program to prevent morbidity and mortality related to carbon monoxide. This surveillance system, along with the interregional surveillance system of the Toxicovigilance Center, had been evaluated; the assessment concluded that the system was malfunctioning, particularly regarding the definition of reportable cases and the reporting procedure. Following this evaluation, few corrective measures were implemented, and the Picardy system continued to operate under the same conditions: - Reporting is initiated by the emergency services that treated the patient (fire department, SMUR, SAMU, hospital emergency departments, or private emergency practitioners). - Reports are centralized by the Departmental Directorates of Health and Social Affairs (DDASS) of the Somme, Oise, and Aisne. To assess the comprehensiveness of the system and improve its effectiveness, the heads of these services requested an evaluation of the comprehensiveness of the carbon monoxide poisoning reporting system to the DDASS for the year 2001. The main objective of the study is to evaluate the surveillance system established in the Picardy region in terms of the completeness of reports by comparing the information transmitted by the Picardy DDASS for the year 2001 with data from other available sources. (Context and Objective)