ABSTRACT In the present study, response of corpuscles of Stannius in the freshwater fish, Notopterus notopterus was investigated by exposing the fish to calcium rich water and copper sulfate containing water. In calcium chloride exposed, the CS cells are active characterized by vesicular nucleus in the majority of cells with cytoplasmic degranulation. After exposure to copper sulfate at a concentration of 30 ppm in the water, the CS cells were active with varying sizes of nuclei along with cytoplasmic vacuoles. Although majority of cells is having vesicular nucleus with clear chromatin material, in some cells the nuclei are small with less chromatin. The cytoplasm is light eosinophilic with vacuolar appearance. The above characteristic of CS cells indicates that the cells become active and hypotrophied in copper sulfate exposed fishes. The results from the above studies suggests that calcium and copper content of the medium plays significant role in stimulating and activating corpuscles of Stannius cells in the freshwater fish, Notopterus notopterus.