A freshwater fish species, silverside (Odontesthes bonariensis) from Mar Chiquita coastal lagoon, Argentina, was analyzed for concentrations of several organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs) in liver, gonads, mesenteric fat and muscle, and the contents of the digestive tract over several stages of sexual maturation. PCBs and OCs were detected at ng/g concentrations (wet weight) in pooled samples, with levels generally in the order of fat > liver > gonad > muscle, reflecting the differences in tissue lipid content. Lipid-normalized concentrations of the analytes were relatively consistent among tissues, except for significantly higher concentrations of PCBs (e.g., 447.7 ng/g lipid wt) in the ovaries of female silverside. DDT and its metabolites, gamma-HCH, and several insecticides from the cyclodiene class, including endosulfan and endosulfan sulfate, were the predominant OCs in fish tissues and the contents of the digestive tract, reflecting recent and past pesticide use in this region. The ratio of OCs to PCBs in all tissues was >1; consistent with contamination of the region with OC pesticides. However, PCBs were dominated by penta- and hexachlorobiphenyls, which is consistent with direct (i.e. , nonatmospheric) inputs. Biomagnification of penta- and hexachlorobiphenyl PCB congeners was noted in fish tissues relative to the contents of the digestive tract. Total OC and PCB concentrations in the ovaries and muscle of silverside were below concentrations associated with reproductive impairment in fish or the limits for human consumption, respectively.