This document summarizes a study on the histopathological changes in tissues of the freshwater fish Cyprinus carpio due to exposure to certain chlorinated hydrocarbon pesticides. Chronic bioassay studies were conducted using DOT, BHC, aldrin and dieldrin at sublethal concentrations. Histopathological analysis found accumulation of pesticides in various tissues after prolonged exposure, with different tissues showing different accumulation levels. Exposure resulted in histopathological changes to vital organs like gills, liver, kidneys, and intestines. Changes included swelling, thickening, and destruction of gill filaments; abnormal fatty degeneration and enlargement in liver; abnormalities in kidney tissue including vacuolated cells in glomerul