In the present work an attempt has been made to evaluate the toxic effect of Furadan (a carbamate pesticide) on histopathological and histochemical changes in the intestine of a fresh water mud eel, Macrognathus aculeatus (Bloch) at sublethal concentrations (0.6, 0.80 and 0.90 ppm) for 10 and 20 days expsoures. Such treatment caused the changes in normal architectural plan of intestine. The orientation of villi was disturbed and villi were disorganised, reduced, flattened and inflated at the base. The villi tips were ruptured leading to the exudation of mucous in the lumen. The lamina propria became fibrous and odema appeared in it. The concentration of the mucosal cells with underlying connective tissue was severed making the mucosa to hand freely into the lumen. Other changes noticed were autolysis of submucosa, highly broken and ruptured villi, histolysis of columnar cells, lymphocytic infilteration and also the hyper activity of mucous cells were obvious. With the use of certain stains such as PAS, Bromophenol blue and Best carmine etc, changes in intensity of stains for carbohydrate, protein and glycogen test have been studied in control and Furadan intoxicated fishes. The details have been discussed in this paper.