Introduction - Following Storm Xynthia on February 28, 2010, a system to monitor psychological consequences was implemented in the post-emergency phase. The objective was to measure and track changes in the use of healthcare services and to ensure that services met the needs for psychological care and prevention. Methods - The monitoring system relied on voluntary healthcare professionals in the municipalities most affected by the floods submitting a completed clinical form for every patient who consulted them and exhibited psychological symptoms directly or indirectly related to Storm Xynthia, regardless of the initial reason for the consultation. Analysis and feedback were provided in the form of a report during the six-month monitoring period. Results - Only specialized care providers participated: medical-psychological centers, psychologists from the dedicated support system (on-call services and telephone helplines), and hospital psychiatrists. A total of 227 cases were reported between April 7 and September 19, 2010. After a high number of cases in the 2nd and 3rd months following the storm, as well as in the 5th month, the number of cases dropped sharply starting in the 6th month. The majority of cases were women (70%) and adults (92% over the age of 20), and more than one-third had a history of psychiatric disorders. The most frequently observed psychological manifestations were depressive symptoms and anxiety disorders, followed by early-stage or established post-traumatic stress disorder. Between the 4th and 8th months after the storm, five feedback reports were sent to healthcare providers and public authorities. The surveillance data enabled adjustments to the activities of the specialized care system. Conclusion - Surveillance made it possible to track the progression and characteristics of cases utilizing both routine and specialized mental health services. Through its rapid implementation and the dissemination of status reports, the surveillance system served as a decision-making tool for healthcare providers. (R.A.)