In April 2008, the Nice University Hospital reported nine cases of measles, including one healthcare worker, to the Departmental Directorate of Health and Social Affairs (DDASS) of the Alpes-Maritimes. An investigation was launched to document the circulation of the virus and to describe the clusters of cases identified in the Provence-Alpes-Côte d'Azur region and in Monaco. Case identification took place from March to May 2008 based on an investigation of the first cases, notifications made to the DDASS, and a search for biologically confirmed cases through laboratories. Thirty-six cases, including 5 healthcare workers, were identified, primarily in the Alpes-Maritimes. Half of the cases were aged 20 years or older. Two clusters of cases involving nosocomial transmission were identified. Following the alert, awareness-raising efforts regarding diagnosis, the implementation of preventive measures, and case reporting through mandatory reporting were carried out in hospital settings. The immune status of healthcare workers was verified through medical records, serobank data, or new specimens. The debriefing meeting that followed this investigation once again emphasized the importance of raising healthcare workers’ awareness regarding the diagnosis and rapid reporting of measles cases, and of updating their vaccination status in accordance with current recommendations, including for individuals born before 1980 who are not immune. Furthermore, when measles virus circulation is suspected, patients presenting with a febrile rash should be placed in isolation upon arrival at a healthcare facility pending diagnostic evaluation. (R.A.)