In September 2002, teachers at the Joliot Curie school complex (Aubervilliers, Seine-Saint-Denis) expressed concern about the occurrence, within the school, of cancers and thyroid disorders that had developed between 1988 and 2002 in 18 adults and 2 children. The epidemiological investigation confirmed an excess of cancers among the teachers (9 cases) but not among the students. The excess of cancers is primarily explained by gynecological cancers (6 cases): 1 excess case of ovarian cancer and 3 excess cases of breast cancer compared to the general population. For breast cancers, a comparison with data specific to female teachers in the Île-de-France region reduced the excess to 2 cases, as risk factors are more common in this population group. There was no excess of thyroid disorders. Radioactivity measurements conducted at the school and in the neighborhood ruled out exposure to ionizing radiation. The environmental investigation did not identify any environmental risk factors: the school was not built on a contaminated site, and no industrial or artisanal activity could have caused major environmental pollution or significant population exposure. These findings also apply to the nearby former military site, which was the subject of a thorough investigation. The cluster of gynecological cancers observed is therefore mainly explained by individual risk factors and random fluctuations in the occurrence of cancers. (R.A.)