A spectrophotometric method based on the liberation of carbon disulfide is suitable for the determination of ethylenebis(dithiocarbamate) (EBDC) residues on apples. Homogenization of samples before analysis initiates rapid breakdown of EBDC, resulting in low recoveries. Thermal conversion of mancozeb to ethylenethiourea (ETU) in the course of apple processing was investigated. The formation of ETU from EBDC could be reduced by lowering the pH value. The presence of an antioxidant (ascorbic acid or cysteine) significantly diminished the yields of ETU after heating, but they inhibited its subsequent decomposition. The rate of ETU formation did not correspond to a relatively rapid disappearance of the parent compound. The levels of ETU residues in the canned baby food originating from contaminated apples were evaluated after a 9-months storage period: the reduction of ETU amounts varied from 26 to 70%.