Abstract: The present research is carried out to observe the biochemical effect of Malathion on the glucose, glycogen and protein levels. The effects of LC₅₀ of commercial malathion (Hindustan Insecticide Ltd.) C₁₀H₁₉O₆PS₂ were tested in the laboratory on the larvae of rice moth Corcyra cephalonica. The rice moth Corcyra cephalonica (Stainton) (Lepidoptera-Pyralidae) is an important stored grain pest in Asia and South America. Its larval stages causes serious damage to rice, gram, sorghum, maize, ground nut, cotton seeds, peanuts, linseeds, raisins, nutmeg, chocolates, biscuits, wheat, coffee, cocoa, beans and milled products. Already contaminated or damaged stored food grains by C. cephalonica were collected from Dhule Dist. Maharashtra State, India and were reared in the laboratory conditions. The standard culture of this insect was maintained in the laboratory on normal dietary medium composed of coarsely ground jowar (Sorghum vulgare) mixed with 5% (w/w) yeast powder at 26±1°C and 93±5% Relative Humidity (RH). Young Corcyra larvae hatched out from the egg within 3-4 days and fed on the grains by webbing. The larval period lasted about 20-25 days and pupation took place inside the web itself moths start emerging after 35-40 days.The objective was to examine the changes in carbohydrate (glucose and glycogen) and protein contents. The larvae were released on treated as well as normal dietary medium. After 24 h 50% mortality was found at 8 ppm dose level. Then, 1/5th of LC₅₀ concentration were mixed with dietary medium and allowed larvae to feed for 168 h the surviving larvae were taken for estimation of glucose, glycogen and protein. After treatment lived larval bodies were used for estimation of carbohydrate (glucose and glycogen) and protein content. Recovery changes were also noted in the remaining lived larvae after 168 h of normal feeding. It was found that the concentration of glucose in normal, treated and recovery samples were 900 μg, 550 μg and 720 μg mL^-1 , respectively while glycogen was 800 μg, 500 μg and 650 μg mL^-1, respectively and protein was 200 μg, 320 μg and 290 μg mL^-1, respectively.