The effect of washing and peeling on the behavior and persistence of chlorpyrifos-methyl, diazinon and phenthoate in cucumber was investigated. The effect of insecticides on carbohydrate, chlorophyll and soluble protein contents as well as the activity of peroxidase and poly phenol oxidase were also studied. After one hour from application, the residues on cucumber were 1.42, 1.71 and 0.53 ppm for chbrpyrifos -methyl, diazinon and phenthoate, respectively. The residues of half -life values (81.50) for the same pestiddes were 23.31, 18.71 and 17.85 in respect. Washing with tap water after one hour from the application removed 31.69 % of chlorpyrifos-methyl, 64.91 % of dlazinon and 26.41 % of phenthoate. The corresponding values after peeling were 95.07 %, 76.02% and 94.32%, respectively. The results revealed that all insectiddes did not show any change In the total contents of carbohydrates, soluble sugars, reducing sugars, non-reducing sugars, diolorophyl, soluble prolien, peroxidase and polyphenal oxidase activity. Phenthoate treatments significantly increased total car bohydrate contents. Diazinon significantly decreased MOl soluble sugars, reducing and non reducing sugars, but Increased significantly the contents of chlorophyl b. On the other hand, chlorpyrifos methyl significantly increased the contents of cholorophyl b.