Toxicological studies of lead nitrate on cornea of the fish, grass carp was investigated. 96 h LC₅₀ of lead nitrate to Ctenopharyngodon idellus was determined by Probit analysis and it was found to be 33.27 mg/l. Toxicopathic corneal lesions were assessed by histopathology and scanning electron microscopy by exposing fish to sublethal concentration of lead nitrate- 11.09 mg/l (1/5^th of LC50) for 15, 30 and 45 days. Histopathological alterations were characterized by sloughing off of the epithelial layer, degeneration of the fibrillar mat of stromal layer, erosion and heavy necrosis of epithelial cells. In addition, wrinkled and shrinked central region, uplifted epithelial layer, appearance of globular structures, detached irregular cells, severely damaged apical region and shrinked microridges were found under scanning electron microscopic studies. The results indicate that lead exposure has adversely affected the vision of the fish, attributable to cellular alterations.