Liza parsia were exposed to 0.05 and 0.01 ppm HgCl₂for 15 days. The treatments resulted in an initial swelling (hypertrophy) of the tubular lining epithelial cells. Thereafter, in proximal segments, the tubular epithelium became nectrotic at several places. These necrosed cells contained eosinophilic hyaline droplets in their cytoplasm. Glomerular capillaries became more permeable and proteinaceous fluid appeared in many Bowman’s capsule. These degenerative changes were more pronounced in the fish maintained at higher concentration of Hg. The probable interactions of heavy metal pollutant with fish immune system have also been discussed.