In April 2007, the InVS regional office in the Nord region was tasked with investigating a suspected cluster of malignant hematological diseases and lymphomas in Aniche, a town with a rich industrial history. The objectives were to confirm or rule out the existence of a spatio-temporal cluster and to identify sites in the environment that could generate exposures potentially linked to it. The standardized incidence ratio (SIR) was calculated for 1984–2006. The results show no excess of cases of acute leukemia (AL) or non-Hodgkin lymphoma (NHL) among adults, nor any excess of NHL cases among children. However, an excess of AL cases among children was found for the periods 1996–2006 (SIR = 5.61 [1.81–13.11]) and 1984–2006 (SIR = 3.37 [1.23–7.34]). Current atmospheric emissions from glassworks are low; however, past localized soil contamination has been confirmed, suggesting that contamination persists in certain areas. A study to assess the health impact of environmental contamination has been launched in an area including Aniche. Other hypotheses can be proposed to explain the excess cases of AL found among children: overestimation of the excess risk due to the a posteriori statistical approach, random variation due to the natural distribution of the disease; furthermore, various hypotheses are currently being investigated: infectious origin, exposure to pesticides as well as to benzene or other substances, in a genetically susceptible population. (R.A.)