The retrospective cancer incidence study conducted around the Gilly-sur-Isère municipal waste incineration plant—initiated amid a crisis following its closure in late 2001—aimed to determine whether there was an excess of cancer cases in the vicinity of the facility. It involved compiling, as comprehensively as possible, a list of cancers occurring between 1994 and 2002 in the population exposed to atmospheric emissions from the incinerator (a study area comprising 30 municipalities, or approximately 48,000 residents), in order to compare the observed incidence with that established by French cancer registries. Medical data were collected from multiple sources: anatomical and cytopathology laboratories, hematology laboratories, medical information departments, and specialized services in hospitals and clinics, primary health insurance funds, private practitioners, and specialized cancer registries. Administrative data were also collected from the admissions offices of healthcare facilities and from the National Health Insurance Fund for Salaried Workers. The majority of cancers identified through these information sources had to be validated by consulting medical records. A total of 2,055 cancer cases were identified. The calculated completeness and validity indicators (number of sources per case, histological confirmation rate, etc.) showed that the quality of the survey was comparable to that of registries. Thus, cancer incidence rates in the study area could be compared to average incidence rates across 7 departments covered by a general cancer registry and having data through 2001, by calculating standardized incidence ratios (SIR) for each cancer site. No significant excess of cases was observed either for all cancers or for the sites most commonly associated with incinerators or dioxins (non-Hodgkin’s malignant lymphomas, soft tissue sarcomas, leukemias). This result did not support the hypothesis of an effect of the incinerator on cancer incidence in this area. Analysis of data from a more exposed sub-area did not alter this conclusion. The results obtained were consistent with the results of other local studies conducted around the facility: a cancer mortality study, a quantitative assessment of health risks, and a study of dioxin contamination in breast milk. It therefore did not appear justified to conduct an analytical epidemiological study to test the hypothesis of a causal link between the incinerator and the occurrence of cancers. However, national multicenter studies on dioxin exposure and cancer incidence around incinerators may aid in the interpretation of local studies. (R.A.)