Losses of malathion postharvest residues were determined in various methods of processing gooseberries, plums, tomatoes, apples, and string beans, as well as after washing the fruits. The approximate losses were: canning, 50% or more; processes with a cooking period of 15 to 20 minutes, 30 to 50%; juice making by pressing or steaming, 70 to 90%; drying at 75 degrees C for 1 to 2 days, 90 to 100%; freezing, 40 to 50%. When fruits were washed in running water for 1 minute, the losses varied from 0 to 79%. When the processed materials were stored at 4 degrees C, practically no malathion was lost.