Following reports of four cases of bladder cancer diagnosed over a short period by a doctor in the town of Espéraza (Aude), an investigation was conducted by the InVS to determine whether there was an excess of bladder cancer cases in the population of Espéraza and its surrounding area and, if this excess was confirmed, to formulate hypotheses regarding one or more possible causes for this cluster of cases, other than chance. The study was conducted as part of a collaborative effort, bringing together various stakeholders within a steering committee. In total, 13 cases of invasive bladder cancer were diagnosed between January 1, 2005, and June 30, 2011, among residents of the study area. Ten to 13 cases were theoretically expected, depending on whether national or local reference data (the Hérault Tumor Registry) were considered. Thus, the epidemiological investigation did not reveal an excess of bladder cancer for the study area and period; the steering committee decided to discontinue the investigations. (R.A.)