Introduction. In March 2012, a doctor reported that four young rugby players in the Dordogne had been diagnosed with cancer and were suspected of having taken "anabolic" substances. The Limousin-Poitou-Charentes Regional Cancer Registry (Cire) and the Aquitaine Regional Cancer Registry (Cire), in collaboration with the Limousin Regional Health Agency (ARS), conducted an investigation to validate the report and verify the existence of a spatiotemporal cluster of cancers. Methods. A standardized questionnaire was developed to collect health information and exposure factors. The sources of information for case validation were the oncologists treating the patients and medical records for deceased cases. The sources of information for environmental factors were medical records, the patient via the attending physician, or a family member. Results. Four different types of cancer were identified: 2 hematologic malignancies (1 Hodgkin’s lymphoma and 1 acute lymphoblastic leukemia), 1 germ cell tumor, and 1 pelvic carcinoma of unknown primary origin. The years of diagnosis spanned an 8-year period. The cases, all male, were aged 16 to 20 at the time of diagnosis. Two of the cases died as a result of their illness. All four cases were high-level rugby players, and two played for the same club. Two cases reside in the same municipality, another about 20 kilometers away, and another in a neighboring department. Three of the four cases for which information could be documented did not have the same occupational activities (or studies). Only one of the three cases for which information could be documented reported having consumed creatine-based dietary supplements. Conclusion. The data collected allow us to rule out the presence of a spatiotemporal cluster due to the different locations of the cancers, the spread of cases over time, and a weak geographical link, as well as the fact that, apart from playing rugby—which is common in this department—no common factors among the four cases were identified. Only one case confirmed creatine consumption. Furthermore, there is no known or established link between the use of creatine-based supplements and the observed pathologies. However, the potential carcinogenic risk, particularly in the long term, to consumer health has not been ruled out by the French Agency for Food, Environmental and Occupational Health & Safety. (R.A.)