Particulate heavy metals and hydrocarbons have been measured in Paris urban area during dry and wet weather periods. A 18 months campaign realised upstream Paris, in the river Seine, has evidenced higher heavy metals concentrations during summer than winter. Summer campaigns demonstrate a strong impact of Paris urban area and its discharges. The direct impact of highly polluted urban overflows into River Seine has been evidenced as a weak immediate but significant retarded discharge of particulate toxic metals. Ratios of significant PAH's allows a better understanding of sources and transport of hydrocarbon in urban areas. Furthermore, relation of these impacts to those observed for heavy metals brings useful information on effects of urban storm drainage.