On Saturday, February 20, 2010, firefighters in the Hérault department reported to the Regional Health Agency that approximately 15 people had experienced abdominal pain, nausea, and vomiting after consuming a cocktail served during a rugby match at the Stade Yves du Manoir (Montpellier). One of these individuals had been taken to the emergency room. Investigations were conducted to confirm the incident, identify the source of contamination, and guide management measures. A case-control study was conducted jointly by DT 34 and the Languedoc-Roussillon Regional Unit of the French Institute for Public Health Surveillance using a standardized questionnaire. Concurrently, laboratory analyses and a veterinary investigation were conducted, including sampling of control dishes and inspection of the caterer’s premises and the stadium. In total, 94 cases and 110 controls were identified among the cocktail party attendees. The epidemiological investigation revealed two waves of the outbreak—an early wave and a late wave—with distinct symptoms and median incubation periods of 3 hours and 30 minutes and 30 hours, respectively. The results of the epidemiological, biological, and veterinary investigations supported the hypothesis that the early cases were poisoned by ingestion of mini-ham hocks contaminated with Staphylococcus aureus (OR=3.75; CI=[1.91; 7.35] p=0.001) and food poisoning in the late cases due to consumption of oysters contaminated with Norovirus (OR=32.22; CI=[7.09; 146.34] p<0.001). This investigation identified the foods and pathogens responsible for this outbreak of foodborne illness. This incident underscored the importance of adhering to hygiene practices in institutional food service and of implementing control measures early on once the results of epidemiological or veterinary investigations are known. (R.A.)