From February to April 2004, several outbreaks of mucosal and skin irritation occurred among staff at the Villejuif City Hall. In early 2005, the phenomenon recurred and led, as in 2004, to the evacuation of part of the premises. In this context and at the request of the city hall, epidemiological and environmental investigations were initiated. A case was defined as any city hall employee reporting at least one irritative symptom during the study period (January 1, 2004, to March 17, 2005) and attributing it to their occupational activity. A standardized questionnaire was administered in person to cases who agreed to participate in the study. Data regarding gender, age, department, and building of employment were collected for all staff members. A descriptive analysis of the cases and a retrospective cohort study were conducted; the data were processed using Epi-Info software version 3.3. Interviews were conducted with local physicians and pharmacists to identify potential cases in the general population. Air quality measurements were taken outdoors near municipal buildings; soil and groundwater samples collected at a nearby construction site were analyzed, and businesses near City Hall were inspected. Measurements of volatile organic compounds, aldehydes, and ketones were taken inside municipal buildings. Seventy people were interviewed. The prevalence rate was 17% in 2004 and 30% in 2005; women were 1.7 times more affected than men. In both 2004 and 2005, the symptoms experienced included signs of irritation and dryness of the mucous membranes, skin symptoms, and general symptoms (fatigue, headaches, etc.). No similar phenomenon occurred during the same period in the general population. No unusual sources or outdoor pollution were identified.Indoor air quality analyses revealed inadequate ventilation and low humidity levels. They did not reveal any abnormal concentrations of pollutants. The symptoms experienced by the staff are mild and in every respect similar to those described in the scientific literature under the name of sick building syndrome. The factors typically associated with this syndrome and found in the municipal offices in Villejuif are inadequate ventilation, low humidity, and difficult working conditions, linked to the care of people in need and an unsuitable office layout. (R.A.)