The toxic effects of cadmium upon the hepatic cells of a freshwater fish were studied. The experiment was developed by the addition of cadmium chloride in the water and histochemical and EM methods were performed. The results showed that acute intoxication induces an increase of lysosomal activity related to the shape, distribution as well as different functional degrees of the organelle condensation. The authors analyze the different situations whose leading alterations of lysosomal behaviour and the probable mechanisms of cadmium action.