Abstrat This study was launched to furnish data on both priority pollutant (PP) occurrence and concentrations in combined sewer overflows (CSOs). Hence, one rain event was studied on 13 sites within the Paris sewer network. For each sample, a total of 66 substances, including metals, polycyclic aromatic hydrocarbons (PAHs), pesticides, organotins, volatile organic compounds, chlorobenzenes, phthalates and alkylphenols were analysed. Of the 66 analyzed compounds, 40 PPs including 12 priority hazardous substances were detected in CSOs. Most metals were present in all samples. Chlorobenzenes and most pesticides were never quantified above the limit of quantification while most of the other organic pollutants but DEHP (median concentration 22 μg.l -1) were found in the μg.l -1 range. For the rain event studied, the pollutant loads discharged by CSOs were evaluated and then compared to the pollutant loads conveyed by the Seine River. Under the hydraulic conditions considered and according to the estimations done, this comparison highlights that CSOs are potentially a significant local source of metals, PAHs and DEHP.