An expcriment was conducted to assess level and duration-of milk contamination as a side effect of spraying: dairy buffalo with diazinon. The experi-ment was.carricd out at the experimental dairy farm, Animal Production Department, Faculty of agriculture, ‘Cairo University. Four dairy buffa-loes were sprayed with diazinon solution (1 ml di-azinon/litter of water) using a motorized spraycr. Three milk samples were collected from cach ani-mal two hours after spraying, thereafter the col-lection was repeated two times at a 24-hour interval.The iesults showed that residues level was thehighest (0.586/ppm) in the first day after spray-ing. Differences among means were only signifi-cant between the Ist day and 2nd and 3rd days.Difference between mean diazinon Ievels in thei,thy 2nd and 3rd days was nol significant. Bodyweight of the cows was a significant source ofvariance on its milk content of diazinon. As bodyweight of the animal increase, its milk is expectedto contain more diazinon residues.