14 C-malathion and stored for nine months under central Anatolian conditions. Enamelware buckets were used for storage in order to simulate the local conditions. The effect of cooking and/or baking of grains after storage on the distribution of 14 C-residues was also determined. MATERIALS AND METHODS 14 C-Malathion with a specific activity of 37 mCi/mmol was purchased from Armersham International Limited, UK. Nonradioactive malathion was obtained from the Plant Protection Institute in Ankara. All reagents used were of analytical grade. The scintillation cocktail was prepared by dissolving 7 g of PPO, 0.05 g of POPOP and 50 g of naphtalene in 1 liter of dioxane. Samples of maize, beans, wheat and barley that had never been treated before with any pesticide were obtained from the Plant Protection Institute in Ankara for this investigation. Analysis of these samples, as described later, indicated that they were free of malathion and/or metabolite residues. Cracked seeds and foreign materials that might affect residue levels were removed by hand (Anderegg and Madisen 1983). The moisture content of the grain was determined by weighing and oven drying 10 g of the seeds for 18 h, at 130 °C. Quantities of 1.5 kg of each sample were treated with 137 µCi 14 C-malathion + 0.75 g of 2% nonradioactiv e malathion dust to give a final concentration of 10 ppm active ingredient. Treated grain samples were stored in enamelware buckets at ambient temperature of 10-30 °C. At these levels no growth of pests and/or other microorganisms was observed during storage.