This thesis explores the toxicokinetic and toxicologic aspects of uranium in fish. Uranium appears to be highly bioaccumulated and bioconcentrated in fish. It spreads all through the whole organism. Nevertheless, its distribution is heterogeneous (gills and liver being the main sites of accumulation).From a toxicologic point of view, we notice perturbations of the antioxidant system (inhibitions of hepatic SOD, CAT and GPx activities; depletion of total GSH) and of the cholinergic system (inhibition/over-activation of brain AChE). Genotoxic effects also appear in red blood cells, hepatocytes and gonadic cells. The kinetics of these biochemical perturbations depend on the radiological activity of uranium, responses appearing earlier with increasing delivered activity. Histological effects (differing in types depending on delivered radiological activity) are also observed (in gills and muscles).