The content of glycosinolates in crucifers and other plants and their behavior during ensiling was studied. It was found that up to 80% of glycosinolates decompose during ensiling. Acidification of the mass with formic acid somewhat slows down the decomposition of glycosinolates. Decomposition of glycosinolates does not occur during ensiling of clover, which, in the authors' opinion, is explained by the low activity of glycosinolate hydrolases. The evolution of hydrogen sulfide at the start of ensiling of a number of crops was established.