In late January 2009, the Languedoc-Roussillon regional office of the French Institute for Public Health Surveillance was notified by the Parasitology-Mycology Laboratory at the Montpellier Regional University Hospital of 13 cases of toxoplasmosis that had occurred over the course of a few weeks among immunocompetent individuals, the majority of which were acute symptomatic cases. The initial report came from a clinical laboratory. An investigation was conducted to identify the source of the contamination. A descriptive study was carried out, involving active case finding of biologically confirmed cases among laboratories in the study area and the collection of information on case exposure using a standardized questionnaire. In parallel with these investigations, food and veterinary surveys were conducted to identify the foods involved. Between mid-October and late December 2008, 15 cases of acute toxoplasmosis [age: 13–57 years] were identified, a significant increase compared to the number of cases usually observed (2 to 3 cases per year). These cases included 1 man and 14 women (4 of whom were pregnant). Twelve symptomatic cases presented with lymphadenopathy, asthenia, and febrile syndrome. Some of the cases shared a history of consuming raw or undercooked meat, although this risk factor was not confirmed by the results of the dietary and veterinary investigations. An excess of symptomatic cases of toxoplasmosis was confirmed in late 2008 in Montpellier and its immediate surroundings. The occurrence of clusters of acute toxoplasmosis is known but rarely described. The hypothesis of a common food source could not be demonstrated, particularly due to the time lag between the cases’ exposure period and the time when the cluster was identified by the laboratory and subsequently confirmed by a reference laboratory. This case report has, however, highlighted several points regarding the investigation of clusters of toxoplasmosis cases. This type of study may also be of interest for furthering our understanding of the conditions under which such outbreaks occur. (R.A.)